Compressive Structures of the Median Nerve at the Elbow / Estructuras Compresivas del Nervio Mediano en el Codo

SUMMARY: The objective of this study was to analyze the potential for compression of the median nerve (MN) caused by the bicipital aponeurosis (BA), the humeral and ulnar heads of the pronator teres muscle (PTM) and the arcade of the flexor digitorum superficialis muscle (FDS) in recently deceased cadavers. In this analysis 20 forearms of 10 recently deceased adult male cadavers were dissected. Dissections were performed in the institution's autopsy room or anatomy laboratory. The short and long heads of the biceps brachii muscle, as well as the BA were identified in all upper upper limbs. The BA received contribution from the short and long heads of the biceps brachii muscle. In 12 upper limbs the BA was wide and thickened and in 8 it was supported by the MN. In 5 upper limbs, the BA was wide but not very thick, and in 3 it was narrow and not very thick. We identified the existence of the FDS muscle arcade in all dissected upper limbs. A fibrous arcade was identified in 4 forearms, a muscular arcade in 14 and a transparent arcade in 2 upper limbs. In all of them, we recorded that the arcade was in contact with the MN. We recorded the humeral and ulnar heads of the PTM in all dissected upper limbs, with the presence of fibrous beams between them along their entire length. The MN was positioned between the humeral and ulnar heads of the PTM in all upper limbs. In eight upper limbs (40 %), we identified that the BA had thickness and contact with the MN with the potential to cause its compression. Compression between the humeral and ulnar heads of the PTM by the fibrous connections has the potential to cause nerve compression in all upper limbs (100 %). We did not identify that the anatomical structure of the FDS arcade had the potential to cause compression in the MN.

El objetivo de este estudio fue analizar la potencial compresión del nervio mediano (NM) causado por la aponeurosis bicipital (AB), las cabezas humeral y cubital del músculo pronador redondo (MPR) y la arcada del músculo flexor superficial de los dedos (MFS). En este análisis se diseccionaron 20 antebrazos de 10 cadáveres masculinos de individuos adultos fallecidos recientemente. Las disecciones se realizaron en la sala de autopsias o en el laboratorio de anatomía de la Institución. En todos los miembros superiores se identificaron las cabezas corta y larga del músculo bíceps braquial, así como la AB. La AB recibió contribución de las cabezas corta y larga del músculo bíceps braquial. En 12 miembros superiores la AB era ancha y engrosada y en 8 estaba sostenida por el NM. En 5 miembros superiores la AB era ancha pero poco gruesa, y en 3 era estrecha y de menor grosor. Identificamos la existencia de la arcada muscular MFS en todos los miembros superiores disecados. Se identificó una arcada fibrosa en 4 antebrazos, una arcada muscular en 14 y una arcada delgada y transparente en 2 miembros superiores. En todos ellos registramos que la arcada estaba en contacto con el NM. Registramos las cabezas humeral y cubital del MPR en todos los miembros superiores disecados, con presencia de haces fibrosos entre ellas en toda su longitud. El NM estaba situado entre las cabezas humeral y cubital del MPR en todos los miembros superiores. En ocho miembros superiores (40 %), identificamos que la AB era gruesa y tenía contacto con el NM con potencial para causar su compresión. La compresión entre las cabezas humeral y ulnar del MPR, por las conexiones fibrosas, tiene el potencial de causar compresión nerviosa en todos los miembros superiores (100 %). No identificamos que la estructura anatómica de la arcada MFS tuviera el potencial de causar compresión del NM.

[Rare nerve compression neuropathies] / Seltene Nervenkompressionssyndrome.

UNCOMMON NERVE COMPRESSION SYNDROMES: In regard to the complex anatomical relationship of peripheral nerves and muscles, tendons, fasciae as well as their long course within those anatomical structures and additional close contact to bony structures, they are prone to suffer from local compression syndromes. Hence creating a vast majority of entrapment syndromes - well described in literature for almost every single nerve. The purpose of this article is to give an overview of symptoms, signs, diagnostic studies and treatment options, addressing especially the less known syndromes. Compression syndromes of the upper arm and shoulder region include the suprascapular nerve syndrome the compression of the axillary nerve within the spatium quadrilaterale and the compression of the long thoracic nerve at the chest wall. The upper extremity offers a variety of infrequent entrapment syndromes, as the pronator teres syndrome and anterior interosseus syndrome, both resulting from pressure to the median nerve in the forearm. Compression neuropathy in the course of the radial nerve in the distal upper extremity is also known as supinator syndrome. Guyon's canal syndrome is the ulnar side equivalent to the well-known carpal tunnel syndrome. In the case of a Cheiralgia paresthetica, a compression of a sensory branch of the superficial radial nerve can be seen. In the lower extremities, a variety of nerves especially in the groin and thigh area can be compressed as they pass through the narrow spaces between the abdominal muscles or underneath the inguinal ligament. Compression of the lateral femoral cutaneous nerve is the most common syndrome. Compression syndromes of the femoral and obturator nerves are most often iatrogenic. Pain around the knee, especially the lateral part and following orthopedic procedures of the knee, can arise from a compression or a lesion of a small infrapatellar branch of the saphenous nerve. Another probably underdiagnosed syndrome is piriformis syndrome, resulting from an entrapment of the sciatic nerve as it passes through certain muscular structures. In the distal lower extremity, the peroneal and tibial nerves can be compressed at multple sites, clinically known as peroneal nerve paralysis resulting from nerve compression around the fibular head, the anterior and posterior tarsal tunnel syndrome, and Morton's metatarsalgia.

Accuracy of suprascapular notch cross-sectional area by MRI in the diagnosis of suprascapular nerve entrapment syndrome: a retrospective pilot study.

BACKGROUND: Previous studies have demonstrated that morphological changes in the suprascapular notch are closely associated with suprascapular nerve entrapment syndrome (SNES). Thus, we hypothesized that the suprascapular notch cross-sectional area (SSNCSA) could be a good diagnostic parameter to assess SNES. METHODS: We acquired suprascapular notch data from 10 patients with SNES and 10 healthy individuals who had undergone shoulder magnetic resonance imaging (S-MRI) and had no evidence of SNES. T2-weighted coronal magnetic resonance images were acquired from the shoulder. We analyzed the SSNCSA at the shoulder on S-MRI using our image-analysis program (INFINITT PACS). The SSNCSA was measured as the suprascapular notch, which was the most affected site in coronal S-MRI images. RESULTS: The mean SSNCSA was 64.50 ± 8.93 mm2 in the control group and 44.94 ± 10.40 mm2 in the SNES group. Patients with SNES had significantly lower SSNCSA (P < 0.01) than those in the control group. Receiver operating curve analysis showed that the best cut-off of the SSNCSA was 57.49 mm2, with 80.0% sensitivity, 80.0% specificity, and an area under the curve of 0.92 (95% CI [0.79, 1.00]). CONCLUSIONS: The SSNCSA was found to have acceptable diagnostic properties for detecting SNES. We hope that these results will help diagnose SNES objectively.

Microvascular neural blood flow assessment for a chronic nerve compression neuropathy mouse model by fluorescein angiography.

BACKGROUND AND AIMS: Intraoperative fluorescence angiography with indocyanine green or fluorescein is used in ophthalmology and neurosurgery. However, there are few reports on the use of fluorescence angiography for peripheral neuropathy. This study aimed to assess the validity of fluorescein angiography (FAG) for peripheral nerve entrapment neuropathy. METHODS: We used an established model of chronic nerve compression (CNC) neuropathy in C57BL/6 mice by entrapping their left sciatic nerve with a silastic tube. Mice were assigned to the uninjured group (control), two-week CNC neuropathy group, four-week CNC neuropathy group, or six-week CNC neuropathy group. We then performed FAG to assess neural blood flow and quantified the peak of the luminance at the compression site with luminance analysis software. Following FAG, histological examinations using an anti-fluorescein antibody and Masson's trichrome staining were performed to evaluate the area of fluorescein distribution and epineural fibrosis. RESULTS: The luminance in the CNC neuropathy groups was significantly lower than that in the control group. Histological analysis revealed the fluorescein positive areas in the CNC neuropathy groups were significantly smaller than that in the control group, and the epineural fibrosis areas in the CNC neuropathy groups were significantly larger than that in the control group. CONCLUSION: We observed a significant decline of luminance in the CNC neuropathy groups, and the histological assessment was consistent with this result. FAG was found to be a valid method for assessing CNC neuropathy in mice.

Prevalence and severity of neurovascular compression in hemifacial spasm patients.

Hemifacial spasm is typically caused by vascular compression of the proximal intracranial facial nerve. Although the prevalence of neurovascular compression has been investigated in a cohort of patients with classical trigeminal neuralgia, the prevalence and severity of neurovascular compression has not been well characterized in patients with hemifacial spasm. We aimed to investigate whether presence and severity of neurovascular compression are correlated to the symptomatic side in patients with hemifacial spasm. All patients in our study were evaluated by a physician who specializes in the management of cranial nerve disorders. Once hemifacial spasm was diagnosed on physical exam, the patient underwent a dedicated cranial nerve protocol magnetic resonance imaging study on a 3 T scanner. Exams were retrospectively reviewed by a neuroradiologist blinded to the symptomatic side. The presence, severity, vessel type, and location of neurovascular compression along the facial nerve was recorded. Neurovascular compression was graded as contact alone (vessel touching the facial nerve) versus deformity (indentation or deviation of the nerve by the culprit vessel). A total of 330 patients with hemifacial spasm were included. The majority (232) were female while the minority (98) were male. The average age was 55.7 years. Neurovascular compression (arterial) was identified on both the symptomatic (97.88%) and asymptomatic sides (38.79%) frequently. Neurovascular compression from an artery along the susceptible/proximal portion of the nerve was much more common on the symptomatic side (96.36%) than on the asymptomatic side (12.73%), odds ratio = 93.00, P < 0.0001. When we assessed severity of arterial compression, the more severe form of neurovascular compression, deformity, was noted on the symptomatic side (70.3%) much more frequently than on the asymptomatic side (1.82%) (odds ratio = 114.00 P < 0.0001). We conclude that neurovascular compression that results in deformity of the susceptible portion of the facial nerve is highly associated with the symptomatic side in hemifacial spasm.

The role of pruriceptors in enhancing sensitivity to pruritogens in a murine chronic compression model of dorsal root ganglion.

Chronic pruritus is a symptom that commonly observed in neurological diseases. It has been hypothesized that the chronic pruritus may result from sensitization of itch-signaling pathways but the mechanisms remain obscure. In this study, we established a mouse model of chronic compression of dorsal root ganglion (CCD) and injected various pruritogenic and algogenic agents intradermally to the calf skin ipsilateral to the compressed dorsal root ganglion (DRG). Compared to the naïve mice, a significant increase in itch-related behaviors was observed in the CCD mice after the injection of pruritogens including histamine and BAM8-22, but not after the injection of capsaicin, although all the above agents evoked enhanced pain-related behaviors toward the injected site. In addition, we investigated if pruritogen-evoked activities of DRG neurons were enhanced in this model. In vivo calcium imaging revealed that compressed DRG neurons exhibited enhanced responses to histamine and BAM8-22. Immunoflorescent staining also showed that the histamine receptor H1 and the capsaicin receptor TRPV1 were significantly upregulated in DRG neurons. Our findings indicated that the sensitization of primary pruriceptive neurons may underlie the enhanced itch sensation after chronic compression of DRG in the mice, and may play a role in chronic pruritus in neurological diseases.

A Rare Intracranial Collision Tumor of Meningioma and Metastatic Uterine Adenocarcinoma: Case Report and Literature Review.

BACKGROUND: A collision tumor is a rare entity consisting of 2 histologically distinct tumor types (benign or malignant) in the same anatomic location. This can occur from a tumor-to-tumor metastasis or as a result of 2 adjacent intracranial tumors colliding and growing together. To our knowledge, this is the first reported case of collision tumor with confirmed meningioma and uterine adenocarcinoma. Multiple mechanisms have been proposed for the facilitative growth of collision tumors, including local epigenetic signaling. Clinically, it is important to consider collision tumors in the differential diagnosis of a rapidly growing intracranial lesion in the setting of systemic cancer to provide optimal surgical and postoperative management. CASE DESCRIPTION: A 78-year-old, right-handed woman with a known 10-year history of stable meningioma presented for evaluation of a right sphenoid wing lesion. She had recently completed treatment of uterine papillary serous carcinoma with no evidence of disease on follow-up imaging. On presentation, there was significant progression of the meningioma resulting in brain compression and right third nerve palsy. The patient underwent urgent resection of the lesion. Pathology demonstrated a collision tumor with a combination of metastatic uterine papillary serous carcinoma and meningioma. CONCLUSIONS: It is important to consider a collision tumor when a patient with a benign intracranial lesion presents with rapid progression, even in the context of a systemic cancer that rarely metastasizes to the brain. Appropriate histopathologic assessment is crucial in these cases and can have a significant impact on treatment plan and prognosis.

Longitudinal Changes in the Retinal Microstructures of Eyes With Chiasmal Compression.

OBJECTIVE: To test the hypothesis that there was a temporal change in the retinal microstructure after decompression surgery for chiasmal compression, the 1-year longitudinal changes in the inner and outer retinal thickness after decompression surgery were analyzed using spectral-domain optical coherence tomography (SD-OCT) with linear mixed-effects models. METHODS: SD-OCT was obtained from 87 eyes with chiasmal compression and compared to 100 healthy controls. The preoperative and 1-year postoperative longitudinal changes in the retinal layer thickness were measured. The thickness of each of the following retinal layers was analyzed: the macular retinal nerve fiber layer (RNFL), the ganglion cell layer (GCL), the inner plexiform layer (IPL), the inner nuclear layer, the outer plexiform layer, the outer nuclear layer, and the photoreceptor layer. RESULTS: The RNFL, GCL, and IPL showed thinning at a rate of 1.068 µm/y (95% confidence interval [CI], 0.523, 1.613), 1.189 µm/y (95% CI 0.452, 1.925), and 1.177 µm/y (95% CI 0.645, 1.709), respectively, after decompression surgery. The preoperative thickness of the intraretinal layer was associated with postoperative visual field recovery (RNFL, odds ratio [OR] 1.221, 95% CI 1.058, 1.410; GCL, OR 1.133, 95% CI 1.024, 1.254; and IPL, OR 1.174, 95% CI 1.002, 1.376). CONCLUSIONS: The changes in retinal microstructure persisted and progressed in eyes with chiasmal compression after decompression surgery. The findings provide insight into the biological and anatomical sequelae following chiasmal compression. The preoperative thickness of the inner retinal layers was associated with postoperative visual field recovery.

Exploring the Morphology of Anterior Interosseous Nerve and Relating It to Its Clinical Conditions.

AIM: To study topography and variability in the origin of anterior interosseous nerve; to identify the branching pattern of the anterior interosseous nerve supplying the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus muscles. MATERIAL AND METHODS: The present study included 70 formalin-fixed upper limbs of adult human cadavers. The origin of the anterior interosseous nerve was categorized into 3 types. The morphometric data obtained in this study were represented as mean± SD and the dimensions were given in millimeter. The measurements were compared statistically by using 'EZR software, version 1.38, 2019'. The 'paired t-test' was applied and the 'p' value less than 0.05 was considered as statistically significant. RESULTS: It was observed that the origin of the anterior interosseous nerve was extremely variable. It was ranging from the midepicondylar point of the elbow joint up to as below as 86mm from it. The distance of its origin from the midpoint of the pronator teres muscle ranged between 70 mm above the pronator teres muscle to 22 mm below it. In one of the forearms, the median nerve supplied the medial two tendons of the FDP, instead of the ulnar nerve. CONCLUSION: The present study provided additional information about the origin, topography, and distribution of the anterior interosseous nerve. The data will provide further insight into the causes of nerve compression syndromes. It will also help in planning the surgical approach into the distal humerus, elbow joint, and proximal ends of radius and ulna, without causing any nerve injury.

Muscle Fascia Changes in Patients with Occipital Neuralgia, Headache, or Migraine.

SUMMARY: In an ongoing effort to understand the pathogenesis of occipital neuralgia/headache/migraine, it is critical to describe the anatomical/tissue changes encountered during surgery. Greater occipital nerve anatomical studies mainly focus on the greater occipital nerve course through muscle/fascial planes and interaction with the occipital vessels. However, structural soft-tissue changes have not been described in detail. Anecdotally, trapezius fascia is thickened at the greater occipital nerve trigger site. This study further investigates this observation. Patients undergoing greater occipital nerve decompression surgery were enrolled prospectively in this observational study (n = 92). Tissue changes were recorded intraoperatively. The resulting data were examined. Trapezius fascia was more than 3 mm thick and appeared fibrotic in 86 patients (94 percent), whereas semispinalis muscle appeared normal in all subjects. The greater occipital nerve was macroscopically abnormal, defined as edematous, flattened, and discolored in 29 cases (32 percent). The occipital artery interacted significantly with the greater occipital nerve in 88 percent of cases. The authors conclude that the tissue structure is abnormal in patients undergoing greater occipital nerve decompression surgery. This is the first study that describes the prevalence of thickened and fibrotic appearing trapezius fascia at the occipital trigger site, a phenomenon encountered in the vast majority of patients (94 percent). This structural anomaly has a resemblance to thickened fascial tissues seen in other nerve compression syndromes, and could be related to microtrauma/overuse or actual trauma in the head and neck region.

Facial Nerve Indentation in Hemifacial Spasm: An Analysis of Factors Contributing to the Formation of and Consequent Effects Associated with Indentation.

BACKGROUND: An indentation, designating a furrowed hole on the facial nerve, has been used in many studies for locating pathophysiology and assessing relevant clinical outcomes after microvascular decompression for hemifacial spasm (HFS). In this study, we sought to elucidate the contributing factors forming indentation on the facial nerve and the consequent effect of having indentation on the clinical course. METHODS: We divided the patients into 2 groups: group A, the patients who had no indentation on the root exit zone of the facial nerve; and group B, the patients who had an indentation. Demographic data, intraoperative findings, and clinical outcomes were analyzed from retrospective review of the medical records. RESULTS: Of the 132 patients, 47.0% had an indentation on the facial nerve. Our statistical analyses showed that the preoperative symptom period, compression location, and compression pattern were associated with the occurrence of the indentation. Also, we showed that HFS reappearance developed more frequently in patients in group B, who needed more time for the resolution of HFS. The final clinical outcome was less influenced by the existence of the indentation, although it was slightly poorer for group B than for group A. CONCLUSIONS: The indentation on the facial nerve was associated with longer duration of symptoms, the presence of compression in the proximal segment of the root exit zone, and loop-type pattern of compression. More patients with indentation experienced the HFS reappearance phenomenon, which lasted longer than in those who had no indentation.

Comparison of MR findings of acute traumatic peripheral nerve injury and acute compressive neuropathy in a rat model.

PURPOSE: The treatment strategy is different for acute traumatic peripheral nerve injury and acute compressive neuropathy. This study aimed to compare magnetic resonance imaging (MRI) features of acute traumatic peripheral nerve injury and acute compressive neuropathy in a rat model. MATERIALS AND METHODS: Twenty female Sprague-Dawley rats were divided into two groups. In the crush injury group (n = 10), the unilateral sciatic nerve was crushed using forceps to represent acute traumatic peripheral nerve injury. In the compression injury group (n = 10), the unilateral sciatic nerve was ligated using silk to represent acute compressive neuropathy. The MRI of eight rats from each group were acquired on postoperative days 3 and 10. Fat-suppressed T2-weighted images were acquired. Changes in the injured nerve were divided into three grades. A Fisher's exact test was used to compare the changes in the nerves of the two groups. Histological staining and a western blot analysis were performed on one rat in each group on day 3. Neurofilament, myelin basic protein (MBP), and p75NTR staining were performed. Expression of neurofilament, MBP, p75NTR, and c-jun was evaluated by western blot analysis. RESULTS: MR neurography revealed substantial nerve changes in the compression injury group compared with the crush injury group at two-time points (p = 0.001 on day 3, p = 0.026 on day 10). The histopathological analysis indicated the destruction of the axon and myelin, mainly at the injury site and the distal portion of the injury in the crush injury group. It was prominent in the proximal portion, the injury site, and the distal portion of the injury in the compression injury group. The degree of axonal and myelin destruction was more pronounced in the compression injury group than in the crush injury group. CONCLUSION: MR neurography showed prominent and long-segmental changes associated with the injured nerve in acute compressive neuropathy compared with acute traumatic peripheral nerve injury.

Optical Coherent Tomography Predicts Long-Term Visual Outcome of Pituitary Adenoma Surgery: New Perspectives From a 5-Year Follow-up Study.

BACKGROUND: Compressive optic neuropathy is the most common indication for transsphenoidal surgery for pituitary adenomas. Optical coherence tomography (OCT) is a useful visual assessment tool for predicting postoperative visual field recovery. OBJECTIVE: To analyze visual parameters and their association based on long-term follow-up. METHODS: Only pituitary adenoma patients with abnormal visual field defects were selected. A total of 188 eyes from 113 patients assessed by visual field index (VFI) and 262 eyes from 155 patients assessed by mean deviation (MD) were enrolled in this study. Postoperative VFI, MD, and retinal nerve fiber layer (RNFL) thickness were evaluated and followed up. After classifying the patients into normal (>5%) and thin (<5%) RNFL groups, we investigated whether preoperative RNFL could predict visual field outcomes. We also observed how RNFL changes after surgery on a long-term basis. RESULTS: Both preoperative VFI and MD had a linear proportional relationship with preoperative RNFL thickness. Sustained improvement of the visual field was observed after surgery in both groups, and the degree of improvement over time in each group was similar. RNFL thickness continued to decrease until 36 mo after surgery (80.2 ± 13.3 µm to 66.6 ± 11.9 µm) while visual field continued to improve (VFI, 61.8 ± 24.5 to 84.3 ± 15.4; MD, -12.9 ± 7.3 dB to -6.3 ± 5.9 dB). CONCLUSION: Patients with thin preoperative RNFL may experience visual recovery similar to those with normal preoperative RNFL; however, the probability of normalized visual fields was not comparable. RNFL thickness showed a strong correlation with preoperative visual field defect. Long-term follow-up observation revealed a discrepancy between anatomic and functional recovery.

Ultrasound-Guided Injections at the Lateral Femoral Cutaneous Nerve: The Inguinal Ligament as a Barrier.

BACKGROUND: Ultrasound-guided perineural injections at the lateral femoral cutaneous nerve (LFCN) may confirm the correct diagnosis and provide symptom relief in meralgia paresthetica. Although correct visualization of the nerve is generally described as feasible, failure rates of the procedure may be as high as 30%. OBJECTIVES: This study investigated the spread of injected fluids in ultrasound-guided perineural injections at the LFCN. The aim of the study was to evaluate whether the inguinal ligament impedes the distribution of injected fluids along the course of the LFCN. STUDY DESIGN: We used a descriptive research design. SETTING: Research was conducted at an anatomical research facility. METHODS: In fresh, nonembalmed cadavers, 2 mL of ink were injected with ultrasound-guidance at the LFCN below the inguinal ligament. The course of the nerve was then dissected to show the extent of nerve staining. RESULTS: Spread of the injected ink proximal to the inguinal ligament was found in 67.65% of specimens, while the ink did not pass the inguinal ligament in 32.35%. Concerning proximal spread, specimen body mass index was not of any relevance. LIMITATIONS: This cadaver study is only a simulation of the real clinical setting and does not allow any insight into the efficacy of the injection in living patients. CONCLUSIONS: The inguinal ligament is a barrier in the distribution of injected fluids in about one-third of specimens. This might be a major cause of failure in ultrasound-guided injections. The results from our study are in line with previously published failure rates and our findings might provide the anatomic basis to advance injection techniques. KEY WORDS: Cadaver study; injection; lateral femoral cutaneous nerve; LFCN; meralgia paresthetica; nerve entrapment; sonography; ultrasound.

The oculomotor neurovascular conflict: Literature review and proposal of management.

BACKGROUND: The Oculomotor nerve (OCN) lies in a close relationship with large arteries inside the basal cisterns. Therefore, it may be compressed by vascular malformations or aneurysms. Nevertheless, the compression is not always related to pathologic conditions. Indeed, some cases of neurovascular conflicts of the OCN have been described in the literature. METHODS: A case of neurovascular conflict of the OCN resolved after steroid treatment is reported. Additionally, a systematic literature review of those cases was performed. RESULTS: OCN palsy due to a neurovascular conflict has been described as acute or chronic persistent palsy, or with an intermittent presentation. Symptoms result from compression, although asymptomatic compression is not uncommon. Surgical treatment, pharmacological treatment, and observation have been reported as options in the literature. Microvascular decompression was employed effectively in some cases of OCN neurovascular conflict. Nevertheless, other cases were treated successfully with steroids (persistent presentation) and carbamazepine (intermittent presentation). A management algorithm based on the results of the literature review is proposed. CONCLUSIONS: Treatment options for OCN neurovascular conflicts and their results are heterogeneous. Based on the literature review, the pharmacological treatment seems to be the most appropriate first-line approach, reserving surgery for refractory cases. Collecting clinical information about new cases will allow defining treatment standards for this rare condition.

Nerve and Muscle Abnormalities.

Muscle atrophy in shoulders with rotator cuff tendon tears is a negative prognosticator, associated with decreased function, decreased reparability, increased retears after repair, and poorer outcomes after surgery. Muscle edema or atrophy within a neurologic distribution characterizes denervation. Because most nerve entrapments around the shoulder are not caused by mass lesions and show no nerve findings on routine MR imaging sequences, pattern of muscle denervation is often the best clue to predicting location of nerve dysfunction, which narrows the differential diagnosis and guides clinical management. The exception is suprascapular nerve compression in the spinoglenoid notch caused by a compressing cyst.

Loop characteristics and audio-vestibular symptoms or hemifacial spasm: is there a correlation? A multiplanar MRI study.

AIM: We investigated if loop characteristics correlate with audio-vestibular symptoms or hemifacial spasm in patients with a vascular loop in the root entry zone (VII and VIII) and in the internal auditory canal. MATERIALS AND METHODS: A retrospective, multicenter study analyzed 2622 consecutive magnetic resonance imaging (MRI) scans of the cerebellopontine angle of patients with asymmetric audio-vestibular symptom or hemifacial spasm; patients' symptoms were confirmed by clinical tests. MRIs displaying vascular loops visible in the axial view were analyzed using multiplanar reconstruction. We evaluated (1) depth of penetration of the loop into the internal auditory canal (IAC); (2) largest diameter of the vessel; (3) nerve(s) involved in the vascular impingement, position of the loop relative to such nerve(s) and number of contacts between vessel and nerve(s); (4) length of such contact. The loop metrics described above were correlated with the patients' audio-vestibular symptoms and hemifacial spasm. RESULTS: Three hundred ninety-nine patients displayed a loop visible in the MRI axial view and out of them only 118 displayed a direct contact between loop and nerve. The cochlear nerve was involved in a contact in 57.7%. Loops in direct nerve contact had a calibre > 0.85 mm, were located in the middle portion of the IAC, and correlated with vertigo (p = 0.002), tinnitus (p = 0.003), and hemifacial spasm (p < 0.001). Asymmetric sensorineural hearing loss (SNHL) correlated with number of contacts (p < 0.001) and length of contact (p < 0.05). The contact was asymptomatic in 41.5% of patients. CONCLUSION: Loop characteristics may help predict whether a vascular impingement is responsible for a symptom and guide the physician to select the best treatment. KEY POINTS: • A vascular loop in the internal auditory canal was observed in 18-20% of the patients in this study; whether a loop can be responsible for a compressive syndrome is still unclear in particular referred to the vestibulocochlear nerve. • Compression by a loop on the facial nerve causes hemifacial spasm; compression by a loop on the cochlear or vestibular nerve may cause audio-vestibular symptoms. • In patients with a loop, the loop calibre, the loop position, and the number of loop-nerve(s) assessed via the multiplanar MRI reconstruction technique may help assess whether the patient will manifest audio-vestibular symptoms or hemifacial spasm.