Extreme Lateral Supracerebellar Infratentorial Approach: Surgical Anatomy and Review of the Literature.

OBJECTIVE: The extreme lateral supracerebellar infratentorial (ELSI) approach has the potential to access several distinct anatomical regions that are otherwise difficult to reach. We have illustrated the surgical anatomy through cadaveric dissections and provided an extensive review of the literature to highlight the versatility of this approach, its limits, and comparisons with alternative approaches. METHODS: The surgical anatomy of the ELSI has been described using 1 adult-injected cadaveric head. Formalized noninjected brain specimens were also dissected to describe the brain parenchymal anatomy of the region. An extensive review of the literature was performed according to each targeted anatomical region. Illustrative cases are also presented. RESULTS: The ELSI approach allows for wide exposure of the middle and posterolateral incisural spaces with direct access to centrally located intra-axial structures such as the splenium, pulvinar, brainstem, and mesial temporal lobe. In addition, for skull base extra-axial tumors such as petroclival meningiomas, the ELSI approach represents a rapid and adequate method of access without the use of extensive skull base approaches. CONCLUSIONS: The ELSI approach represents one of the most versatile approaches with respect to its ability to address several anatomical regions centered at the posterior and middle incisural spaces. For intra-axial pathologies, the approach allows for access to the central core of the brain with several advantages compared with alternate approaches that frequently involve significant brain retraction and cortical incisions. In specific cases of skull base lesions, the ELSI approach is an elegant alternative to traditionally used skull base approaches, thereby avoiding approach-related morbidity.

Spontaneous regression of a clival chordoma. Case report.

In this case report, we present a rare and previously unreported case of spontaneous regression of a histologically consistent clival chordoma. At the time of diagnosis, imaging demonstrated a T2 hyperintense and T1 isointense midline skull base mass, centered in the nasopharynx, with scalloping of the ventral clivus consistent with a chordoma measuring 3.1 × 1.9 × 3.0 cm (8.84 cm3). On pre-operative imaging 2 months later, with no intervening therapy, the mass had regressed by 61.7% to a size of 2.3 × 2.1 × 1.4 cm (3.38 cm3). The patient self-administered several herbal supplements and animal oils which may have contributed to tumor regression. The purpose of this report is to document this rare occurrence and provide a comprehensive description of the case details and list of the various medications, herbs, and supplements used prior to this rare event.

Laser Interstitial Thermal Therapy to the Posterior Fossa: Challenges and Nuances.

BACKGROUND: Posterior fossa tumors are rare in adults and pose a challenge to treat due to the bony contour of the posterior fossa, complex anatomical structures including deep venous sinuses, and the proximity of the fourth ventricle and brain stem. We describe our experience with laser interstitial thermal therapy (LITT) for the management of brain metastases and radiation necrosis of the posterior fossa. METHODS: We retrospectively analyzed 13 patients with metastases and radiation necrosis of the posterior fossa managed with LITT. RESULTS: Thirteen patients with histopathologically confirmed radiation necrosis (n = 5) and metastases (n = 8) of the posterior fossa underwent LITT. The median preoperative tumor was 4.66 cm3, and median postoperative ablation cavity volume was 6.29 cm3. The median volume of the ablation cavity was decreased to 2.90 cm3 at a 9-month follow-up. The median volume of peritumoral edema was 12.25 cm3, which fell to a median of 5.77 cm3 at 1-month follow-up. The median progression-free survival was 7 months (range, 3-14 months) and the mean overall survival was 40 months (range, 2-49 months) after LITT. There were no intraoperative complications. One patient experienced palsy of the seventh and eighth cranial nerves on follow-up, attributable to LITT. CONCLUSIONS: Lesions of the posterior fossa are challenging to treat given their proximity to the dura and venous sinuses. Our findings demonstrate that LITT ablation may be a safe and feasible option for metastases and radiation necrosis of the posterior fossa. Larger studies are needed to confirm the efficacy of this approach.

Laser Interstitial Thermal Therapy for Posterior Fossa Lesions: An Initial Experience.

BACKGROUND: The application of laser interstitial thermal therapy (LITT) for intracranial lesions in the posterior fossa tumors remains challenging due to the smaller size of this compartment as well as the thickness and angle of the occipital bone. In this study, we reviewed our experience with this treatment modality for posterior fossa lesions. METHODS: We retrospectively reviewed our series of 8 patients with posterior fossa tumors treated with LITT from an Institutional Review Board-approved brain tumor database (2012-2017) of more than 200 cases at our institution. RESULTS: The 8 patients underwent LITT targeting 3 metastases, 2 pilocytic astrocytomas, 2 zones of radiation necrosis after radiosurgery, and 1 glioblastoma (GBM). The mean preoperative lesion volume was 4.35 cm3. A 6 months postsurgery, the mean lesion volume had decreased from 9.64 cm3 to 5.72 cm3. Two of the tumors (the GBM and a metastatic adenocarcinoma) progressed after 8.5 and 7.5 months, respectively, with mortality after 1.1 and 1.6 years, respectively. Surgical resection was performed in a patient with metastatic adenocarcinoma tumor at 7.7 months after LITT. All other lesions remained stable or were diminished at a median follow-up of 14.8 months (range, 0.4-37.5 months). Magnetic resonance imaging (MRI) on the first postoperative day, showed an increase in mean tumor-related edema volume from 9.45 cm3 to 14.10 cm3. After a postoperative follow-up of at least 1 month, this mean decreased to 8.70 cm3. One case each of transient partial unilateral sixth cranial nerve palsy, superficial wound infection, and a late obstructive hydrocephalus were noted postoperatively. No mortality was associated with the procedure. CONCLUSIONS: LITT is a safe and feasible treatment modality even in challenging locations like the posterior fossa. However, surgical indications should be tailored for each individual patient based on the size and location of tumor.

Novel Use of the Leksell Gamma Frame for Stereotactic Biopsy of Posterior Fossa Lesions.

BACKGROUND: Stereotactic transcerebellar biopsies of brainstem tumors have often been reported. The Leksell frame or Cosman-Roberts-Wells frame is often used in transcerebellar approaches. However, to access lesions via the cerebellum, these frames should be secured as inferiorly on the cranium as possible, which can require exaggerated neck flexion and limit the flexible trajectory to the target. To overcome these disadvantages, we have devised a new way to use the Leksell frame for transcerebellar approaches. METHODS: The frame was fixed to the upper part of the head and arc support by attaching the frame upside down, which gives surgeons a wide operative field and permits flexible trajectory planning. RESULTS: Under local anesthesia, the surgery was performed in a sitting position. Air was observed in the target site on postoperative computed tomography and magnetic resonance imaging, which confirmed that a specimen had been successfully sampled from the site as planned. CONCLUSIONS: Our devised transcerebellar approach provided a generous operative field and a flexible trajectory, which enabled minimally invasive biopsy of a posterior fossa lesions to be performed in a short amount of time with the patient under local anesthesia.

Dural arteriovenous fistula (D-AVF): a rare cause of symmetrical bithalamic changes with free diffusivity changes.

We report a rare case of an encephalopathic presentation of a posterior fossa dural arteriovenous fistula with concomitant florid symmetrical bithalamic free diffusivity changes on MRI in a previously healthy individual. We describe the structural and functional imaging findings and the role of catheter angiography in diagnosis, prognostication and the timing and strategy in the management of this challenging vascular entity.

Preoperative and postoperative neurological, neuropsychological and behavioral impairment in children with posterior cranial fossa astrocytomas and medulloblastomas: the role of the tumor and the impact of the surgical treatment.

INTRODUCTION: The aim of the present study was to prospectively investigate if a correlation might exist between preoperative and postoperative neurological conditions, neuroradiological/intraoperative findings and results of a complete neuropsychological evaluation in children with posterior fossa medulloblastomas and astrocytomas. MATERIALS AND METHODS: Of the 65 children admitted at the Pediatric Neurosurgery of the UCSC of Rome between January 2005 and October 2009, 41 were selected; the only two exclusion criteria were represented by age under 24 months and severe neurological conditions, seen that in both cases it would not have been a possible reliable evaluation. All children underwent a preoperative and immediate postoperative complete MR study. Hydrocephalus was graded on the Evans score; brainstem infiltration was defined on intraoperative findings. Neuropsychological assessment consisted of a battery of tests tailored on the patient's age, cognitive level, and level of cooperation. Post operative neuropsychological evaluation was performed at a mean time of 2.5 min (2 mos, max 4.5 mos) from the operation, before any eventually needed adjuvant treatment (i.e., chemotherapy, radiotherapy). RESULTS: Concerning neurological status, we found a statistically significant relation between the presence of oculomotor impairment and both verbal fluency deficits (p = 0.044) and imagery disorders (p = 0.03); also, the presence of ataxia/dysmetria was significantly correlated to attention dysfunction (p = 0.01) and, more tightly, to planning dysfunction (p = 0.006). For neuroradiological/intraoperative features, Intelligence Quotient (IQ) impairment was significantly correlated to the intraoperative evidence of tumor infiltration of the brainstem (p = 0.003), a severe hydrocephalus at diagnosis (p = 0.001) and the histological diagnosis of medulloblastoma (MB) (p = 0.002). For selective skills, a significant correlation was found between linguistic processing deficits and the evidence of dentate nuclei infiltration (blindly defined on MR); procedural memory defects and imagery disorders related to the severity of the hydrocephalus (p = 0.02), infiltration of the brain stem (p = 0.01) and a histological diagnosis of MB (p = 0.01). After surgery no patient showed a worsening of his/her cognitive profile; the relationships between clinical, intraoperative, and radiological findings were substantially confirmed. DISCUSSION: Our results support the hypothesis that when present, neuropsychological impairment is already present at diagnosis and that the most statistically significant factors, which might be related with cognitive deficits in the preoperative as well as in the postoperative period, are tumor infiltration of the brainstem, the severity of hydrocephalus, and a histological diagnosis of MB.

[Isotretinoin embryopathy. Report of one case]. / Embriopatía por isotretinoína: Un daño evitable.

Retinoic acid is a widely used drug in the treatment of cystic acne. It has teratogenic effects that depend on the gestational period in which it is used. We report a seven months old female whose mother was exposed to retinoic acid in both pre-gestational and gestational periods. She had a retardation of psychomotor development and a brain MRI showed frontal atrophy and a malformation of the posterior fossa. We discuss the mechanisms of the teratogenic effects of retinoic acid.

Embriopatía por isotretinoína: Un daño evitable / Isotretinoin embryophaty: Report of one case

Retinoic acid is a widely used drug in the treatment of cystic acné. It has teratogenic effects that depend on the gestational period in which it is used. We report a seven months of female whose mother was exposed to retinoic acid in both pregestational and gestational periods. She had a retardation of psychomotor development and a brain MRI showed frontal atrophy and a malformation of the posterior fossa. We discuss the mechanisms ofthe teratogenic effeets of retinoic acid.

Hyperbaric oxygen therapy (HBO) for the treatment of an epidural abscess in the posterior fossa in an 8-month-old infant.

Epidural abscesses in children are extremely rare, especially in the posterior fossa. In some cases antibiotic therapy and surgical drainage are insufficient for complete healing. We present the case of an 8-month-old boy who developed an epidural abscess in the posterior fossa after repeated surgical procedures for retrocerebellar arachnoid cysts and hydrocephalus. We decided to use adjuvant hyperbaric oxygen therapy (HBO) to avoid removal of the bone and the existing ventriculoperitoneal shunt. In this way osteomyelitis, potentially leading to bone removal and shunt infection, could be prevented. HBO is a relatively safe, noninvasive and cost-effective therapy to improve healing of chronic and deep-seated wound infections. To our knowledge HBO has never been used before in such a young child in neurosurgery. Multidisciplinary management is recommended to optimize treatment.

Imaging of sellar and parasellar lesions.

The sellar and parasellar region is an anatomically complex area where a number of neoplastic, infectious, inflammatory, developmental and vascular pathologies can occur. Differentiation among various etiologies may not always be easy, since many of these lesions may mimic the clinical, endocrinologic and radiologic presentations of pituitary adenomas. The diagnosis of sellar lesions involves a multidisciplinary effort, and detailed endocrinologic, ophthalmologic and neurologic testing are essential. CT and, mainly, MRI are the imaging modalities to study and characterise normal anatomy and the majority of pathologic processes in this region. We here provide an overview of the most relevant MRI and CT characteristics together with clinical findings of pituitary tumors, vascular, inflammatory and infectious lesions found in the sellar/parasellar region in order to propose an appropriate differential diagnosis.

Phosphaturic mesenchymal tumor with symptoms related to osteomalacia that appeared one year after tumorectomy.

A 45-year-old man was admitted to our hospital because of bone pain and hypophosphatemia. He had undergone surgery 2 years previously for a "benign unclassified mesenchymal tumor" in the skull, but there were no clinical symptoms related to osteomalacia. His laboratory examination revealed low serum phosphate, high alkaline phosphatase, and normal calcium levels. The diagnosis of tumor-induced osteomalacia due to phosphaturic mesenchymal tumor mixed connective tissue variant (PMTMCT) was made by re-examining the pathologic specimens. Oral supplementation with phosphate and 1-25-dihydroxyvitamin D relieved his clinical symptoms and laboratory values returned to normal. However, subcutaneous administration of octreotide had no clinical effect. Clinicians and pathologists should be aware of the existence of PMTMCT especially nonphosphaturic or asymptomatic variants of this disorder.

Diagnostic value of vestibular evoked myogenic potentials in cerebellar and lower-brainstem strokes.

BACKGROUND: Vestibular evoked myogenic potentials (VEMPs) provide assessment of vestibular function. They consist in picking up compound muscle action potentials in the sternocleidomastoid (SCM) muscles in response to auditory stimulation of the vestibulum. VEMP testing has found application mainly in peripheral vestibular disorders, whereas reports about VEMPs in central vestibular lesions are rather scarce. AIMS OF THE STUDY: Based on the physiological connections between the cerebellum and the vestibular nuclei, we investigated the influence on VEMPs of cerebellar and lower-brainstem strokes. We examined whether or not this method may be suitable as a clinical tool for the evaluation of the extent of cerebellar strokes. PATIENTS AND METHODS: Nineteen patients with cerebellar ischemic stroke and 15 patients with lower-brainstem ischemic stroke (11 in the pons, four in the medulla) were included. The latencies and amplitudes of P13 and N23 in both groups of patients were compared with those obtained in a control group of 53 normal individuals. RESULTS: VEMP responses were obtained in all patients and controls. At the group level, mean peak latencies and amplitudes, and the number of subjects with significantly deviant values did not differ between patients and controls. There were no latency or amplitude differences ipsilaterally or contralaterally to the lesion. At the individual level, there was no correlation between laterality of lesion and that of P13 or N23 abnormalities in patients with cerebellar strokes; however, there were two patients (one pontine, one medullar stroke) who presented P13 and N23 latency abnormalities ipsilaterally to the lesion. CONCLUSION: Cerebellar strokes do not influence VEMPs. Moreover, despite previous reports, we were unable to find at a group level any statistically significant VEMP changes in patients with lower-brainstem strokes as compared with controls. Therefore, VEMPs do not appear a suitable tool for assessment of brainstem integrity in patients with posterior fossa strokes. However, they could constitute a sensitive method for documentation of involvement of the central vestibular pathways in patients with brainstem stroke.

MR-guided laser-induced thermotherapy of the infratemporal fossa and orbit in malignant chondrosarcoma via a modified technique.

A 76-year-old patient presented with a recurrent mass of a malignant chondrosarcoma in the right infratemporal fossa and in the left maxillary sinus with orbital invasion. The patient was treated with a palliative intention with MR-guided laser-induced thermotherapy using a modified applicator technique. Following treatment clinical symptoms improved and MRI revealed complete laser-induced tumor necrosis.

Nimodipine-induced improved survival rate of facial motor neurons following intracranial transection of the facial nerve in the adult rat.

OBJECT: Neuronal survival is an important factor in the achievement of functional restitution after peripheral nerve injuries. Intracranial tumors or trauma may cause patients to exhibit a temporary or permanent facial nerve palsy. Nimodipine, which acts as an antagonist to L-type voltage-gated calcium channels, has been shown to be neuroprotective in various lesion models of the central and peripheral nervous systems. The aim of the present study was to evaluate the effect of nimodipine on motor neuron survival in the facial motor nucleus following intracranial transection of the adult rat facial nerve. METHODS: The facial nerve was cut intracranially in the posterior cranial fossa. Nimodipine was administered orally preoperatively for 3 days and postoperatively for up to 1 month, after which the number of neuronal profiles was quantified. The glial reaction was studied in the facial nucleus for up to 1 month by using immunocytochemical analysis. There was a significantly larger proportion of surviving motor neurons 1 month postinjury in animals treated with nimodipine (61+/-6.7%) in comparison with untreated animals (26.8+/-11.3%). Immunocytochemical analysis showed an increase in the amount of OX42 (microglia), ED1 (macrophages), and anti-glial fibrillary acidic protein (astrocytes) ipsilateral to the nerve injury; however, there was no difference between the two experimental groups of animals 2 to 28 days after surgery. CONCLUSIONS: The authors propose a neuroprotective role for nimodipine, which may be useful as a "cranial nerve protective agent" following insults such as head injury or skull base surgery.

Venous hypertension associated with a posterior fossa dural arteriovenous fistula: another cause of bithalamic lesions on MR images.

We report a case of a posterior fossa arteriovenous fistula (AVF) with bithalamic hyperintensity of MR images. The thalamic abnormality improved after surgery, suggesting reversible venous hypertension as the pathogenesis of the finding, as opposed to infarction. This manifestation of a posterior fossa AVF should be considered in the differential diagnosis of bilateral thalamic disease.

Monitoring and predicting ototoxic damage using distortion-product otoacoustic emissions: pediatric case study.

Young children undergoing cisplatin chemotherapy are known to be at risk for progressive sensorineural hearing loss. Early detection of such hearing loss is important for providing management options. However, in ill and/or young children, behavioral audiometry may not be sufficiently precise to detect the early stages of hearing loss. This case illustrates that distortion-product otoacoustic emissions (DPOAEs) may be an appropriate cross-check measure to supplement and confirm pediatric behavioral data. Perhaps more importantly, this study suggests that DPOAEs may have the potential to predict the earliest stages of progressive hearing loss before such changes are seen in audiometric thresholds.