Combined expansion and STED microscopy reveals altered fingerprints of postsynaptic nanostructure across brain regions in ASD-related SHANK3-deficiency.

Synaptic dysfunction is a key feature of SHANK-associated disorders such as autism spectrum disorder, schizophrenia, and Phelan-McDermid syndrome. Since detailed knowledge of their effect on synaptic nanostructure remains limited, we aimed to investigate such alterations in ex11|SH3 SHANK3-KO mice combining expansion and STED microscopy. This enabled high-resolution imaging of mosaic-like arrangements formed by synaptic proteins in both human and murine brain tissue. We found distinct shape-profiles as fingerprints of the murine postsynaptic scaffold across brain regions and genotypes, as well as alterations in the spatial and molecular organization of subsynaptic domains under SHANK3-deficient conditions. These results provide insights into synaptic nanostructure in situ and advance our understanding of molecular mechanisms underlying synaptic dysfunction in neuropsychiatric disorders.

Characterization of tumor remnants in intraoperative MRI-assisted microscopic and endoscopic transsphenoidal resection of less invasive pituitary adenomas.

INTRODUCTION: Intraoperative magnetic resonance imaging (iMRI) improves the intraoperative detection of adenoma remnants in transsphenoidal surgery. iMRI might be redundant in endoscopic pituitary surgery in non-invasive tumors (Knosp 0-2) due to a superior visualization of anatomical structures in the periphery of the sella turcica compared to the microscopic technique. We identified the anatomical location of tumor remnants in iMRI and evaluated risk factors for secondary resection after iMRI and hereby selected patients with pituitary adenomas who may benefit from iMRI-assisted resection. METHODS: We conducted a retrospective monocenter study of patients who underwent iMRI-assisted transsphenoidal surgical resection of pituitary adenomas at our department between 2012 and 2020. A total number of 190 consecutive iMRI-assisted transsphenoidal surgeries of pituitary adenomas graded as Knosp 0-2 were selected for analysis. Exclusion criteria were missing iMRI availability or pathologies other than adenomas. Of these 190 cases, 46.3% (N = 88) were treated with microscopic, 48.4% (N = 92) with endoscopic, and 5.3% (N = 10) with endoscopic-assisted technique. Volumetric measurement of preoperative, intraoperative, and postoperative tumor extension was performed. Demographic data, tumor characteristics, and MRI features were evaluated. Additionally, analysis of adenoma remnants identified by iMRI was performed. RESULTS: An additional resection after iMRI was performed in 16.3% (N = 31). iMRI helped to reach gross total resection (GTR) in 83.9% (26/31) of these cases. False-positive resection was found in 1 patient (0.5%). Multivariable logistic analysis identified tumor volume (OR = 1.2, p = 0.007) recurrence (OR = 11.3, p = 0.002) and microscopic technique (OR = 2.8, p = 0.029) as independent risk factors for additional resection. Simultaneously, the endoscopic technique was significantly associated with GTR as evaluated by iMRI (OR = 2.8, p = 0.011) and postoperative MRI (OR = 5.8, p = 0.027). The detailed analysis of adenoma remnants on iMRI revealed the suprasellar location in a diaphragm fold, penetrating tumor above the diaphragm, or undetected invasion of cavernous sinus as well as in case of microscopic resection tumor location outside the line of sight as the main reasons for incomplete resections. CONCLUSION: Tumor volume, recurrence, and microscopic technique were identified as independent predictors for additional resection in patients with Knosp 0-2 adenomas. iMRI might increase the extent of resection (EOR) safely even after the endoscopic visualization of the sella with very low risk for false-positive findings. Remnants of tumors hidden within the diaphragmic folds, intrathecally, or behind the infiltrated wall of cavernous sinus not recognized on preoperative MRI were the most common findings in iMRI.

Diagnostic reliability of the Berlin classification for complex MCA aneurysms-usability in a series of only giant aneurysms.

BACKGROUND AND OBJECTIVE: The main challenge of bypass surgery of complex MCA aneurysms is not the selection of the bypass type but the initial decision-making of how to exclude the affected vessel segment from circulation. To this end, we have previously proposed a classification for complex MCA aneurysms based on the preoperative angiography. The current study aimed to validate this new classification and assess its diagnostic reliability using the giant aneurysm registry as an independent data set. METHODS: We reviewed the pretreatment neuroimaging of 51 patients with giant (> 2.5 cm) MCA aneurysms from 18 centers, prospectively entered into the international giant aneurysm registry. We classified the aneurysms according to our previously proposed Berlin classification for complex MCA aneurysms. To test for interrater diagnostic reliability, the data set was reviewed by four independent observers. RESULTS: We were able to classify all 51 aneurysms according to the Berlin classification for complex MCA aneurysms. Eight percent of the aneurysm were classified as type 1a, 14% as type 1b, 14% as type 2a, 24% as type 2b, 33% as type 2c, and 8% as type 3. The interrater reliability was moderate with Fleiss's Kappa of 0.419. CONCLUSION: The recently published Berlin classification for complex MCA aneurysms showed diagnostic reliability, independent of the observer when applied to the MCA aneurysms of the international giant aneurysm registry.

The evolution of invasive cerebral vasospasm treatment in patients with spontaneous subarachnoid hemorrhage and delayed cerebral ischemia-continuous selective intracarotid nimodipine therapy in awake patients without sedation.

Cerebral vasospasm (CV) and delayed cerebral ischemia (DCI) are major factors that limit good outcome in patients with spontaneous subarachnoid hemorrhage (SAH). Continuous therapy with intra-arterial calcium channel blockers has been introduced as a new step in the invasive treatment cascade of CV and DCI. Sedation is routinely necessary for this procedure. We report about the feasibility to apply this therapy in awake compliant patients without intubation and sedation. Out of 67 patients with invasive endovascular treatment of cerebral vasospasm due to spontaneous SAH, 5 patients underwent continuous superselective intracarotid nimodipine therapy without intubation and sedation. Complications, neurological improvement, and outcome at discharge were summarized. Very good outcome was achieved in all 5 patients. The Barthel scale was 100 and the modified Rankin scale 0-1 in all cases at discharge. We found no severe complications and excellent neurological monitoring was possible in all cases due to patients' alert status. Symptoms of DCI resolved within 24 h in all 5 cases. We could demonstrate the feasibility and safety of selective intracarotid arterial nimodipine treatment in awake, compliant patients with spontaneous SAH and symptomatic CV and DCI. Using this method, an excellent monitoring of neurological function as well as early detection of other complications is possible. It might be an important step in the risk reduction of invasive CV therapy to improve the outcome with CV and DCI after SAH in selected patients.

Interobserver variability of the House-Brackmann facial nerve grading system for the analysis of a randomized multi-center phase III trial.

BACKGROUND: Evidence of a high interobserver variability of the subjective House-Brackmann facial nerve grading system (HBGS) would justify cost- and time-consuming technological enhancements of objective classifications for facial nerve paresis. METHOD: A total of 112 patients were recruited for a randomized multi-center trial to investigate the efficacy of prophylactic nimodipine treatment in vestibular schwannoma (VS) surgery. For the present investigation both treatment groups were pooled for the assessment of facial nerve function preoperatively, in the early postoperative course and 1 year after the surgery. Facial nerve function was documented photographically at rest and in motion and classified according to the HBGS by three independent observers (neurosurgeon, neurologist, ENT) and by the investigator of each center. RESULTS: Interobserver variability was considerably different with respect to the three time points depending upon the severity of facial nerve paresis. Preoperative facial nerve function was normal or only mildly impaired (HB grade I or II) and was assessed consistently in 97%. Facial nerve function deteriorated during the early postoperative course and was subsequently documented without dissent in only 36%, with one grade difference in 45%, two grade difference in 17% and three grade difference in 2%. One year after surgery, facial nerve function predominantly improved resulting in a consistent assessment in 66%. Differing ratings were observed in 34% with one grade deviation in 88% and of two grades in 12%. Patients with differing ratings of two or more grades exhibited considerably worse facial nerve function (p < 0.001). CONCLUSIONS: The HBGS produced comparable results between different observers in patients with normal or only mildly impaired facial nerve function. Interobserver variability increased depending on the severity of facial nerve paresis. The results suggest that the HBGS does not promote uniformity of reporting and comparison of outcomes in patients with moderate or severe facial nerve paresis.

Intraoperative high-resolution ultrasound and contrast-enhanced ultrasound of peripheral nerve tumors and tumorlike lesions.

The diagnostic workup and surgical therapy for peripheral nerve tumors and tumorlike lesions are challenging. Magnetic resonance imaging is the standard diagnostic tool in the preoperative workup. However, even with advanced pulse sequences such as diffusion tensor imaging for MR neurography, the ability to differentiate tumor entities based on histological features remains limited. In particular, rare tumor entities different from schwannomas and neurofibromas are difficult to anticipate before surgical exploration and histological confirmation. High-resolution ultrasound (HRU) has become another important tool in the preoperative evaluation of peripheral nerves. Ongoing software and technical developments with transducers of up to 17-18 MHz enable high spatial resolution with tissue-differentiating properties. Unfortunately, high-frequency ultrasound provides low tissue penetration. The authors developed a setting in which intraoperative HRU was used and in which the direct sterile contact between the ultrasound transducer and the surgically exposed nerve pathology was enabled to increase structural resolution and contrast. In a case-guided fashion, the authors report the sonographic characteristics of rare tumor entities shown by intraoperative HRU and contrast-enhanced ultrasound.

[Interdisciplinary Treatment Of Tumorous And Tumour-Like Lesions Of Peripheral Nerves]. / Interdisziplinäre Behandlung von Raumforderungen in Assoziation zu peripheren Nerven: Tumore und tumorähnliche Läsionen.

Tumorous or tumour-like lesions of peripheral nerves are generally rare, heterogeneous and challenging to diagnose and treat. They may become apparent by a palpable swelling (lump) near nerves, sensory and/or motor deficits, pain to touch or neuropathic pain. In 91% of cases, tumours are benign. The differentiation of entities and their characteristics as well as a function-preserving resection strategy are highly relevant. Misdiagnosis and inadequate treatment can lead to severe deficits and pain syndromes. Benign tumours include schwannomas and neurofibromas, which can occur sporadically but can also be associated with neurogenetic tumour disposition syndromes if they occur more frequently. Rarer benign nerve tumours include perineuriomas, lipomas, aggressive fibrosis (desmoid tumours), paragangliomas and haemangiomas. Ganglion cysts are described as tumour-like lesions. The association of nerve tumours with neurogenetic syndromes and the correct classification of potentially malignant lesions such as MPNST (malignant peripheral nerve sheath tumour) or intermediate stages such as ANNUBPs (atypical neurofibromatous neoplasms with unknown biological potential) pose particular challenges. Interdisciplinarity is highly relevant for clinical treatment and a correct diagnosis. The aim of our work is to provide an overview of the relevant entities, diagnostic evaluation and contemporary treatment strategies based on the current data situation and taking into account the recently published interdisciplinary AWMF S2k guideline "Diagnosis and Treatment of Peripheral Nerve Tumours".

[Functional Outcome of Peripheral Nerve Injury after Pediatric Supracondylar Humerus Fracture: Comparison of Surgical and Conservative Treatment]. / Funktionelle Ergebnisse peripherer Nervenverletzungen nach kindlichen suprakondylären Humerusfrakturen: Vergleich operativer und konservativer Behandlung.

Supracondylar humerus fractures are the most common elbow fractures in children up to 10 years of age. The incidence of associated nerve injuries varies up to 15% depending on the data. Traumatic and iatrogenic lesions mainly affect the ulnar nerve. The regeneration of peripheral nerves is comparatively better in childhood. In the present study, the functional results after surgical and conservative treatment of nerve injuries in children after supracondylar fractures were compared and analyzed for influencing factors. In this retrospective comparative study, clinical data of pediatric nerve injuries following supracondylar humerus fractures treated over a period of 13 years (2008-2021) were analyzed. Children who were treated surgically (neurolysis, autologous reconstruction) due to insufficient clinical/neurophysiological improvement within 6 months after trauma or who were followed up conservatively in case of regression of symptoms within 6 months after trauma were included. All patients underwent multidisciplinary follow-up. 48 patients (26 female/22 male) with nerve injuries were included in this study. All patients had a history of surgical treatment with K- wire fixation due to severe dislocated fractures. The mean age was 7±2 years. The initial symptoms were severe motor deficits in all patients and sensory deficits in 87.5% (n=42). Isolated lesions of the ulnar nerve were most common (n=24, 50%). The nerve was neurolysed in 21 patients and additionally transferred to the volar side in 15. Nerve grafting was performed in 7 children and split repair in 2. Postoperatively, there was a significant improvement in motor function in all patients. Despite comparably severe motor deficits at initial presentation, further 20 children were treated conservatively due to the regression of neurological deficits. They showed comparably good functional results. No serious complications were recorded in either group. The average follow-up time was 377.25±524.87 days. The presented study shows excellent functional results after surgical treatment of pediatric nerve injuries without severe complications. Children with comparatively high-grade lesions at initial presentation have a good chance of complete spontaneous remission even without surgery. For this reason, the indication for surgery in children should be very carefully considered.

[Neuralgic amyotrophy: an inflammatory neuropathy and its surgical treatment]. / Neuralgische Amyotrophie ­ eine entzündliche Neuropathie und ihre operative Behandlung.

BACKGROUND: Neuralgic amyotrophy (NA) is a monofocal or oligofocal inflammatory neuropathy whose incidence has been significantly underestimated. A connection between constrictions and torsions of peripheral nerves with this disease has been increasingly established in recent years. Modern imaging techniques such as high-resolution nerve ultrasound and MR neurography have contributed to a better understanding of the pathophysiology and a better assessment of the prognosis of the disease. This has led to the concept of treating patients with such focal changes surgically in order to improve the prognosis. This review presents current ideas on the pathophysiology, clinical presentation, diagnosis and treatment of the disease. PATIENTS AND METHODS: In a retrospective study, pre-, intra- and postoperative findings of 22 patients with 23 constrictions/torsions of peripheral nerves of the upper extremity were analysed. The patients underwent surgery at a nerve surgery centre over a period of 3.5 years (Dec. 2019-May 2023). The median nerve was most frequently affected (N=9), followed by the suprascapular nerve (N=6) and radial nerve (N=4). The axillary nerve (N=3) and the accessory nerve (N=1) were also involved. Surgical exploration revealed nerve torsions (N=9), nerve constrictions (N=5), fascicular torsions (N=12) and fascicular constrictions (N=9). Depending on the intraoperative findings, epineuriotomies (N=1), epi- and perineuriotomies (N=33), end-to-end sutures (N=2), and one epi- and one perineural suture were performed. RESULTS: After an average follow-up of 10 months (3-28 months), 17 patients were re-examined. All of them reported a clear subjective improvement in motor deficits. Clinically and electromyographically, a reinnervation and significant increase in strength from a pre-existing strength grade of M0 to at least M3 in the vast majority of affected muscles was demonstrated in these patients. SUMMARY: The incidence of NA continues to be underestimated and, in a significant proportion of patients, leads to permanent motor deficits, most likely due to constrictions and torsions of affected nerves. Surgical treatment is recommended as early as possible. Very good results can usually be achieved with epi- and perineuriotomy. In rare cases, end-to-end neurorrhaphy or nerve grafting is required.

[Long-Term Outcomes after Surgery of the Neurogenic Thoracic-Outlet Syndrome in Adolescents]. / Langzeitergebnisse nach Operation des neurogenen Thoracic-Outlet-Syndroms bei Jugendlichen.

BACKGROUND: Neurogenic Thoracic Outlet Syndrome (nTOS) describes a complex of symptoms caused by the compression of neural structures at the upper thoracic outlet. Typical symptoms include pain, numbness and motor weakness of the affected extremity. The incidence of nTOS is 2-3 per 100,000 and is highest between the ages of 25 and 40. There are only a few studies evaluating the surgical outcomes of nTOS in adolescent patients. In particular, there is a lack of long-term data. MATERIALS AND METHODS: In a retrospective study of nTOS cases receiving surgical treatment in our clinic between 2002 and 2021, eight patients between 15 and 18 years of age were included. Demographic data, risk factors, clinical symptoms, clinical functional tests, neurophysiological, radiological and intraoperative findings were evaluated. Postoperative data were recorded using a standardised questionnaire. Decompression of the inferior truncus and the C8 and Th1 nerve roots was performed via a supraclavicular approach. RESULTS: The average duration of symptoms before surgery was two years. Of the eight patients who underwent surgery, six answered the written questionnaire and could be analysed for the study. The average follow-up was nine years (1-18 years). After surgery, all patients experienced pain reduction; three were pain-free in the long run and five no longer required pain medication. Strength improved in all patients, but two patients still had mild motor deficits. Sensory disturbances were reduced in all patients, but residual hypoesthesia persisted in five. With regard to overhead work, half of the patients had no impairment after surgery. All patients were able to work at the time of the survey. Half of the patients pursued their sports activities without impairment, while mild impairment was reported by the other half. CONCLUSION: nTOS in adolescents is a rare compression syndrome. Decompression of the lower parts of the brachial plexus using a supraclavicular approach without resection of the first rib is an adequate treatment. This retrospective study showed that a reduction in pain was achieved in all patients. In some patients, slight sensory and motor disturbances as well as a certain restriction in overhead work persisted. Patients were able to return to sports.

[Rare Compression Syndrome of the Median Nerve due to a Supracondylar Humeral Process and a Ligament of Struthers]. / Seltenes Kompressionssyndrom des N. medianus durch den Processus supracondylaris und das Struthers-Ligament.

INTRODUCTION: A supracondylar process is a bony spur on the distal anteromedial surface of the humerus, and it is considered an anatomical variant with a prevalence of 0.4-2.7% according to anatomical studies. In almost all cases, it is associated with a fibrous, sometimes ossified ligament, which extends from the supracondylar process to the medial epicondyle. This ligament is known in the literature as the ligament of Struthers, named after the Scottish anatomist who first described it in detail in 1854. In rare cases, the supracondylar process can be a clinically relevant finding as a cause of nerve compression syndrome. The median and ulnar nerve can be trapped by the ring-shaped structure formed by the ligament of Struthers and the supracondylar process. CASE REPORT: A 59-year-old patient with symptoms of a cubital tunnel syndrome and additional ipsilateral sensory deficits in his thumb was referred to our clinic. Electroneurography showed no signs of an additional carpal tunnel syndrome. Preoperative x-ray and CT scans of the upper arm revealed a supracondylar process, which led us to suspect an associated entrapment of the median nerve. An MRI scan of the upper arm showed a ligament of Struthers and signs of a related median nerve compression as we initially assumed. We performed a surgical decompression of the median nerve in the distal upper arm and of the ulnar nerve in the cubital tunnel. Intraoperatively, there was evidence of compression of the median nerve due to the supracondylar process and the ligament of Struthers. The latter was cleaved and then resected along with the supracondylar process. Three months after surgery, the patient had no motor or sensory deficits. SUMMARY: The ring-shaped structure formed by the supracondylar process and ligament of Struthers represents a rare cause of compression syndrome of the median and ulnar nerve. Its incidence remains unknown so far. This anatomical variant should be considered a differential diagnosis in case of possibly related nerve entrapment symptoms after ruling out other, more frequent nerve compression causes. Moreover, the supracondylar process should be completely resected including the periosteum during surgery to minimise the risk of recurrence.

Mapping Motor Neuroplasticity after Successful Surgical Brachial Plexus Reconstruction Using Navigated Transcranial Magnetic Stimulation (nTMS).

Brachial plexus reconstruction (BPR) consists of the complex surgical restoration of nerve structures. To further understand the underlying motor cortex changes and evaluate neuroplasticity after a successful surgery, we performed a navigated transcranial magnetic stimulation (nTMS) study mapping the postoperative motor representation of the formerly plegic arm. We conducted a prospective nTMS study mapping the musculocutaneous nerve as a representative, prominent target of BPR including a patient (n = 8) and a control group (n = 10). Measurements like resting motor threshold (RMT), cortical motor area location, and size were taken. Mathematical analysis was performed using MATLAB 2022, statistical analysis was performed using SPSS 26, and nTMS mapping was performed using the Nexstim NBS 5.1 system. Mapping was feasible in seven out of eight patients. Median RMT on the affected hemisphere was 41% compared to 50% on the unaffected hemisphere and they were 37% and 36% on the left and right hemispheres of the control group. The motor area location showed a relocation of bicep brachii representation at the middle precentral gyrus of the corresponding contralateral hemisphere. Motor area size was increased compared to the control group and the patient's unaffected, ipsilateral hemisphere. Understanding cortical reorganization is important for potential future treatments like therapeutic nTMS. The issue of motor neuroplasticity in patients with brachial plexus lesions is worth exploring in further studies.

Health-related quality of life in patients with peripheral nerve tumors: results from the German multicentric Peripheral Nerve Tumor Registry.

Objective: Peripheral nerve tumors (PNTs) are rare diseases. So far, no multicenter data on diagnostics, the efficacy of treatment, long-term outcomes, and health-related quality of life (HRQoL) exist. The establishment of the Peripheral Nerve Tumor Registry (PNTR) in 2015 allows for the systematic analysis of patients with tumors associated with peripheral nerves. The present study aims to investigate the impact of PNT on an individual's HRQoL and the effect of surgery. Methods: HRQoL was pre- and postoperatively assessed by the Euro-Qol-5D-5L (EQ-5D-5L) and Euro-Qol visual analog scale (EQ-VAS) survey in the retrospective and prospective study arm in three active participating study centers. An index was calculated based on the EQ-5D-5L for the quantification of health state (0: worst possible state of health, 1: best possible state of health). The EQ-VAS ranges from 0% (worst imaginable health status) to 100% (best possible health status). Patient characteristics (age, sex), as well as disease (histopathological entity) and treatment (pre- and postoperative symptoms, type of treatment)-specific data, were analyzed. Results: Data from 171 patients from three high-volume centers were included, with schwannoma (70.8%, n = 121) and neurofibroma (15.8%, n = 27) being the most prevalent histopathological diagnoses. Both the median health index value (preoperative: 0.887, n = 167; postoperative: 0.910, n = 166) and the median EQ-VAS (preoperative: 75%, n = 167; postoperative: 85%, n = 166) of the entire cohort regarding all histopathological diagnosis improved significantly after surgical therapy (p < 0.001). Preoperatively, 12.3% (n = 21) reached the highest index score of 1.0 in EQ-5D-5L and 100% in the EQ-VAS score in 5.3% (n = 9) of all patients. Postoperatively, the highest index score of 1.0 and 100% in the EQ-VAS score increased significantly and were achieved in 33.3% (n = 57) and 11.1% (n = 19) of the patients, respectively (p < 0.001). Conclusion: For the first time, our study presents multicenter data on life quality and the effect of surgery in primarily benign peripheral nerve tumors. Early surgery at a specialized center could improve neurological outcomes and, in conclusion, better QoL. In summary, surgical therapy significantly improved the entire cohort's QoL, VAS, and analgesia.

The impact of SARS-Covid-19 pandemic on peripheral nerve surgery - A single centre report.

OBJECTIVE: SARS-Cov-19 pandemic totally changed daily routine work in German hospitals. As hospital capacity was reduced, many surgeries were postponed or even cancelled. On March 25th 2020 the German Society of Neurosurgery (DGNC) published a statement in which urgent non-elective surgeries were defined for each neurosurgical domain, whereas elective interventions were deferred. The present work examines the impact of these Covid strategies focusing on patients with peripheral lesions who were conducted to our department during this period of time. METHODS: All patients who underwent any peripheral nerve surgery at our department from January 2018 until December 2022, were included. The complete range of surgeries including peripheral nerve lesions was examined encompassing compression syndromes, traumatic lesions of brachial plexus, traumatic lesions and tumors of single peripheral nerves. The numbers of surgical procedures were compared before, during and after pandemic. Pearson correlation coefficient was analysed. RESULTS: From 2018 to 2022 the total number of surgical procedures involving peripheral nerves included 2422 procedures. Compression syndromes made up the largest proportion (1433 operations, 59%), followed by peripheral nerve lesions (445 operations, 18%), peripheral nerve tumors (344 operations, 14%) and lesions of the brachial plexus (142 operations, 6%). The average was 40,5 interventions per month, the range was 7-63. Two declines in the number of peripheral nerve surgeries were noted during this period. The first was in April and May 2020 with an average drop of 65% and 41% respectively. In these months the average number of operations was 37. The second decrease was from October 2021 until January 2022, where number of surgeries was reduced by 16%, 36%, 83% and 18% with an average number of 50 operations. Both declines showed a significant and strong correlation with the lower number of compression syndrome treatments (r = 0.952, p < 0.001 and r = 0.968, p < 0.001), while no drop and no significant correlation was found in the treatment of traumatic peripheral nerve injuries (p = 0.769, r = 0.095 and p = 0.243, r = 0.366) and traumatic brachial plexus injuries (p = 0.787, r = 0.088 and p = 0.780, r = 0.09). A weak significant correlation was seen in the treatment numbers of peripheral nerve tumors (p = 0.017, r = 0.672 and p = 0.015, r = 0.67). CONCLUSION: Covid-19 pandemic lead to a significant decrease in the number of nerve decompressions, since, according to the German Society of Neurosurgery, those were considered as elective surgeries.

Case report: Atypical neurofibromatous neoplasm with uncertain biological potential of the sciatic nerve and a widespread arteriovenous fistula mimicking a malignant peripheral nerve tumor in a young patient with neurofibromatosis type 1.

We report an unusual constellation of diseases in a 32-year-old woman with neurofibromatosis type 1 (NF1) diagnosed with the recently described precursor entity of malignant peripheral nerve sheath tumor (MPNST), the so-called atypical neurofibromatous neoplasm with unknown biological potential (ANNUBP) and a large symptomatic cervical arteriovenous fistula. An [18F] 2-Fluoro-2-deoxy-D-glucose PET/CT (FDG-PET/CT) was performed to detect and stage a conspicuous symptomatic cervical tumor. The FDG-PET/CT showed high FDG uptake in one of the multiple known tumorous lesions associated with peripheral nerves. However, no relevant FDP uptake was observed in this affected cervical area. After digital subtraction angiography, the cervical mass turned out to be a widespread arteriovenous fistula of the vertebral artery. This was successfully treated using endovascular embolization. Subsequently, magnet resonance imaging (MRI) of the FDG-positive tumor revealed a well-enhanced homogeneous mass of the sciatic nerve measuring 5.2×2.4×2.8 cm. Microsurgical gross total tumor resection was performed using ultrasound. The final histopathological diagnosis was ANNUBP transformed from neurofibroma. The patient benefited excellently from the surgery; no recurrence or metastasis has been observed since resection. According to imaging, ANNUBP can be characterized as a well-enhanced homogeneous mass on MRI, displaying high uptake on FDG-PET/CT and hypoechogenic in ultrasound.

Rationale and design of the peripheral nerve tumor registry: an observational cohort study.

AIM: Peripheral nerve tumors (PNT) are rare lesions. To date, no systematic multicenter studies on epidemiology, clinical symptoms, treatment strategies and outcomes, genetic and histopathologic features, as well as imaging characteristics of PNT were published. The main goal of our PNT Registry is the systematic multicenter investigation to improve our understanding of PNT and to assist future interventional studies in establishing hypotheses, determining potential endpoints, and assessing treatment efficacy. METHODS: Aims of the PNT registry were set at the 2015 Meeting of the Section of Peripheral Nerve Surgery of the German Society of Neurosurgery. A study protocol was developed by specialists in PNT care. A minimal data set on clinical status, treatment types and outcomes is reported by each participating center at initial contact with the patient and after 1 year, 2 years, and 5 years. Since the study is coordinated by the Charité Berlin, the PNR Registry was approved by the Charité ethics committee (EA4/058/17) and registered with the German Trials Registry (www.drks.de). On a national level, patient inclusion began in June 2016. The registry was rolled out across Europe at the 2019 meeting of the European Association of Neurosurgery in Dublin. RESULTS: Patient recruitment has been initiated at 10 centers throughout Europe and 14 additional centers are currently applying for local ethics approval. CONCLUSION: To date, the PNT registry has grown into an international study group with regular scientific and clinical exchange awaiting the first results of the retrospective study arm.

Perineurioma: A Rare Entity of Peripheral Nerve Sheath Tumors.

OBJECTIVE: Intraneural perineurioma is a rare tumor entity. It is a benign, very slow growing peripheral nerve sheath tumor that typically occurs in children and young adults. Motor deficits and muscle atrophy are classic presenting symptoms, while sensory deficits are rare at the onset of the disease. Recommended treatment strategies are lacking. We have evaluated the clinical follow-up and our experience with treatment of this rare entity. METHODS: A total of 30 patients with intraneural perineuriomas were assessed retrospectively. Demographic data, clinical symptoms, diagnostic examinations, therapy strategies, and clinical outcome were analyzed. Descriptive statistical methods were used for evaluation. RESULTS: The mean age was 22 years. Eleven women and 19 men were affected. The lesion occurred in the area of the upper extremity in 16 patients and in the area of the lower extremity in 14 patients. The most frequently affected nerve was the sciatic nerve, followed by the radial nerve. All patients showed a motor deficit to some extent. Seventy percent (n = 21) revealed atrophy, 43.3% (n = 13) had sensitive deficits, and 17% (n = 5) suffered of pain. Fascicle biopsies were performed in 26 patients (87%). In four patients (13%), the tumor was completely resected and then reconstructed via nerve grafts. Seventy percent of the patients (n = 21) received a magnetic resonance imaging (MRI) within 5 years postoperatively, in which no progress was shown. CONCLUSIONS: To diagnose perineurioma, it is essential to take a biopsy of an enlarged, nonfunctional fascicle. Furthermore, a long-distance epineuriotomy to decompress the hypertrophic fascicle is reasonable. To preserve the nerves' residual function, a complete resection is not recommended. Results after grafting are poor. One reason for this might be residual tumor cells along the nerve that cannot be visualized. Malignant transformation is not yet reported and tumor growth is stable for years.

Thoracic Outlet Syndrome Part I: Systematic Review of the Literature and Consensus on Anatomy, Diagnosis, and Classification of Thoracic Outlet Syndrome by the European Association of Neurosurgical Societies' Section of Peripheral Nerve Surgery.

BACKGROUND: Although numerous articles have been published not only on the classification of thoracic outlet syndrome (TOS) but also on diagnostic standards, timing, and type of surgical intervention, there still remains some controversy because of the lack of level 1 evidence. So far, attempts to generate uniform reporting standards have not yielded conclusive results. OBJECTIVE: To systematically review the body of evidence and reach a consensus among neurosurgeons experienced in TOS regarding anatomy, diagnosis, and classification. METHODS: A systematic literature search on PubMed/MEDLINE was performed on February 13, 2021, yielding 2853 results. Abstracts were screened and classified. Recommendations were developed in a meeting held online on February 10, 2021, and refined according to the Delphi consensus method. RESULTS: Six randomized controlled trials (on surgical, conservative, and injection therapies), 4 "guideline" articles (on imaging and reporting standards), 5 observational studies (on diagnostics, hierarchic designs of physiotherapy vs surgery, and quality of life outcomes), and 6 meta-analyses were identified. The European Association of Neurosurgical Societies' section of peripheral nerve surgery established 18 statements regarding anatomy, diagnosis, and classification of TOS with agreement levels of 98.4 % (±3.0). CONCLUSION: Because of the lack of level 1 evidence, consensus statements on anatomy, diagnosis, and classification of TOS from experts of the section of peripheral nerve surgery of the European Association of Neurosurgical Societies were developed with the Delphi method. Further work on reporting standards, prospective data collections, therapy, and long-term outcome is necessary.

Intraoperative Sodium-Fluorescence Imaging in Peripheral Nerve Sheath Tumors (PNST)-A New Additional Promising Diagnostic Tool.

Background: Through the development and implementation of specific fluorophore filters to microscopes in 2012, sodium fluorescein (SF) is currently experiencing a remarkable renaissance in neurosurgery. The present study examines its intraoperative application during surgical removal of peripheral nerve sheath tumors (PNST) and metastases. Methods: This single-center study includes 10 cases of benign and malignant tumors as well as metastases of peripheral nerves (in total 11 PNST). Their surgical resections were all performed under microscope-based fluorescence with SF, which was administered intravenously (0.5-1.0 mg/kg body weight) during anesthesia induction. Microsurgical tumor removals were filmed and the collected data were retrospectively analyzed via ImageJ. Results: Microsurgical tumor preparation was possible under the usage of fluorophore filter. In seven histological confirmed schwannoma (n = 6 patients) tissue differentiation between tumor mass and not involved fascicles was statistically significant for the colors green and red. Schwannoma maximum mean for green reached 254.7 pixel and 179.4 pixel for red, whereas passing healthy fascicles revealed a maximum mean for green 94.91 and for red 120.76 pixel. One case of neurofibroma achieved lower amount of pixel. Similar to schwannoma, the two MPNST cases showed a strong homogeneous fluorescence (max. mean green 215 pixel and red 124.51) involving the whole nerve segment. Subcutaneous tumor remnants were visualized and therefore resected. Via fascicular nerve biopsy a B-cell lymphoma of the tibial nerve could be detected. SF led to variable stain intensities in single fascicles. The resected fascicle revealed a max mean green of 100.54 pixel, whereas surrounding fascicles came up with max. mean green of 63.0 pixel. Conclusions: Intraoperative SF visualization for PNST is feasible and of low risk. During resection of benign PNST, enhanced tissue differentiation between affected and not affected nerve segments is very useful. Tumor remnants can be detected safely and effectively. Its application during resection of malignant PNST is limited. Due to the infiltrative nature of those tumors, intraneural tissue differentiation is not possible. "Fluorescence-guided" biopsy can be regarded as an additional advantage in PNST surgery. Due to the encouraging experience in our institution SF was established as standard visualization tool in PNST surgery.

Sodium Fluorescein as Intraoperative Visualization Tool During Peripheral Nerve Biopsies.

OBJECTIVE: Owing to technical development of specific fluorophore filters, the neurosurgical application of sodium fluorescein (SF) has regained value in brain tumor surgery. The aim of this study was to determine the usefulness of SF during nerve biopsies. METHODS: This single-center study included 5 cases of nerve biopsies performed under microscope-based fluorescence with SF performed between March 2016 and February 2017. SF was applied intravenously (1 mg/kg body weight). After microsurgical dissection of the involved nerve segment, fluorescence-guided fascicular biopsy was performed. Selection of target fascicles was at the surgeon's discretion and took into account nerve stimulation for preservation of motor function and fluorescence intensity. Correlation to histopathologic examination was examined. Video analysis of intraoperative images comparing target fascicles with intense fluorescent response to adjacent fascicles of the same nerve segment was performed using ImageJ. RESULTS: All patients had motor or sensory deficits. Magnetic resonance imaging findings were similar, depicting long segments of gadolinium enhancement (minimum 11.7 cm). Each biopsy sample was positive resulting in diverse histopathologic results. Digital image analysis revealed a statistically significant difference of the complementary color green (P = 0.0473). CONCLUSIONS: Magnetic resonance imaging is the gold standard in diagnostic work-up of peripheral nerve disorders. Longitudinal nerve thickening with positive contrast enhancement is an unspecific magnetic resonance imaging finding. Various pathologies, such as tumors and inflammatory lesions, may cause this morphologic phenomenon. Nerve biopsies may be needed for diagnostic work-up. Intraoperative SF may help to depict the most affected fascicles and identify target fascicles for biopsy and increase diagnostic certainty of nerve biopsies.