Management of Neonatal Facial Paralysis due to Cerebellopontine Angle Arachnoid Cyst: A Case Report.

Arachnoid cysts are benign, cerebrospinal fluid-filled collections that can be located in the brain or spinal cord. Arachnoid cysts form approximately 1% of all intracranial lesions. They are accepted as arachnoid developmental anomaly and arise from membrane splitting or duplication. Generally, lesion growth causes symptoms because of mass effect or obstruction. Arachnoid cyst growing mechanisms are a largely controversial issue. We report the case of a neonatal female patient who presented with congenital facial paralysis. Magnetic resonance imaging showed a right cerebellopontine angle arachnoid cyst causing severe mass effect on the brain stem. Cyst fenestration and cystocisternal shunt was performed through retrosigmoid suboccipital craniotomy.

Bilateral cerebellopontine arachnoid cyst: A rare entity.

Bilateral cerebellopontine angle (CPA) arachnoid cysts (ACs) are very rare: only one case is reported in literature. Pathogenesis of those cysts is unknown; they are thought to be congenital. The presenting symptoms of CPA AC are frequently nonspecific or otological. The management of ACs of the CPA is controversial. We are reporting two cases of bilateral CPA AC with their pathophysiology and review of literature.

Predictive value of Blink reflex and facial corticobulbar motor evoked potential in cerebellopontine angle tumor surgery.

OBJECTIVE: The current study examined the efficacy of the facial corticobulbar motor evoked potentials (FCoMEPs) and blink reflex (BR) on predicting postoperative facial nerve function during cerebellopontine angle (CPA) tumor surgery. METHODS: Data from 110 patients who underwent CPA tumor resection with intraoperative FCoMEPs and BR monitoring were retrospectively reviewed. The association between the amplitude reduction ratios of FCoMEPs and BR at the end of surgery and postoperative facial nerve function was determined. Subsequently, the optimal threshold of FCoMEPs and BR for predicting postoperative facial nerve dysfunction were determined by receiver operating characteristic curve analysis. RESULTS: Valid BR was record in 103 of 110 patients, whereas only 43 patients successfully recorded FCoMEP in orbicularis oculi muscle. A reduction over 50.3% in FCoMEP (O. oris) amplitude was identified as a predictor of postoperative facial nerve dysfunction (sensitivity, 77.1%; specificity, 83.6%). BR was another independent predictor of postoperative facial nerve deficit with excellent predictive performance, especially eyelid closure function. Its optimal cut-off value for predicting long-term postoperative eyelid closure dysfunction was was 51.0% (sensitivity, 94.4%; specificity, 94.4%). CONCLUSIONS: BR can compensate for the deficiencies of the FCoMEPs. The combination of BR and FCoMEPs can be used in CPA tumor surgery. SIGNIFICANCE: The study first proposed an optimal cut-off value of BR amplitude deterioration (50.0%) for predicting postoperative eyelid closure deficits in patients undergoing CPA tumor surgery.

Intraoperative transcranial facial motor evoked potential monitoring in surgery of cerebellopontine angle tumors predicts early and late postoperative facial nerve function.

OBJECTIVE: We propose a novel method that predicts facial nerve function (FNF) calculated from the drop and recovery of facial motor evoked potential (FMEP) amplitude ratio during the surgery of cerebellopontine angle tumors. METHODS: We enrolled 73 patients with cerebellopontine angle tumor, and used a biphasic, constant current, and suprathreshold stimulation (BCS) protocol to record FMEP of the orbicularis oris. We measured the intraoperative minimum-to-baseline amplitude ratio (MBR), the final-to-baseline amplitude ratio (FBR), and the recovery value (RV). RV was measured by subtracting MBR from FBR. Using those values, we evaluated FNF both at early postoperative (EP) and late postoperative (LP) periods. RESULTS: We successfully obtained 62 FMEP readings. Facial palsies occurred in 22 patients during the EP period, and 14 patients recovered during the LP period. Both MBR and FBR showed a significant correlation with FNF in the EP period. RV showed a good predictive power of FNF recovery during the LP period for the first time. CONCLUSIONS: RV is a new and useful predictor of FNF recovery. MBR can be an intraoperative predictor of FNF in the EP period. SIGNIFICANCE: FNF outcome in the early and late postoperative periods can be predicted by FMEP.

Cerebellopontine angle arachnoid cyst containing ectopic choroid plexus--case report.

We present a rare and interesting case of a cerebellopontine angle cyst containing ectopic choroid plexus tissue in a 26 year-old female. Surgical resection was performed, and histological examination confirmed the presence of choroid plexus in the cyst wall. This is the first reported case of ectopic choroid plexus at the cerebellopontine angle in an adult. We present the case and review the literature.

Growth rate of non-operated meningiomas.

INTRODUCTION: Meningiomas are dural-based brain tumors that are typically histologically benign. Some meningiomas grow slowly or seemingly not at all with planimetric measurement. Volumetric measurement may be more accurate because tumors may grow in different directions than the planimetric axes. METHODS: Twenty-one patients (with 22 tumors) had serial MRI brain scans available for review. We reviewed the charts and measured tumor dimensions on the MRI scans. Relative growth rates were calculated for volume and maximum initial diameter using published formulas. Patient demographics, tumor location, and special radiologic characteristics (calcification, T2 hypointensity, dural tail, mass effect, and midline shift) were compared to the volumetric growth rate. RESULTS: Patients included 17 females and 4 males; age at diagnosis 36 to 74 years (mean 61). Follow-up was 2.08 to 10.83 years (mean 3.64). Most tumors were located in the convexity (27.27 %), sphenoid wing (27.27 %), or cerebellopontine angle (13.04 %). Two meningiomas (9.09 %) demonstrated no growth. The mean relative volumetric growth rate was 5.82 %/year, and planimetric was 2.00 %/year (difference 3.82 %/year, p-value < 0.0001). Convexity location had near significant association with slower relative volumetric growth. There were no significant associations between other tumor locations, age, gender, or radiologic characteristics and volumetric growth. CONCLUSIONS: The mean volumetric growth rate was significantly greater than the planimetric growth rate, suggesting that volumetric measurement conveys more information and is superior in assessing tumor growth. This information could have clinical value in determining the frequency of follow-up imaging and the urgency of surgical intervention.

Continuous and Dynamic Facial Nerve Mapping During Surgery of Cerebellopontine Angle Tumors: Clinical Pilot Series.

OBJECTIVE: To evaluate a new surgical tool combining suction and monopolar neurostimulation (stimulation sucker) for cerebellopontine angle (CPA) tumors. The usefulness for continuous (time) and dynamic (space) facial nerve mapping was studied. METHODS: Patients operated on with the stimulation sucker for a CPA tumor between April 2016 and May 2017 in a tertiary care center were identified. Clinical charts were retrospectively evaluated. The minimum follow-up time of patients was 12 months. RESULTS: The study population included 17 patients with tumor (6 women and 11 men). The age range was from 2 to 77 years (mean age, 45.7 years; standard error of the mean, 22.7 years). Most CPA tumors were large (Koos grade 4) vestibular schwannomas (n = 10); other pathologies included petrous meningioma (n = 1), metastasis (n = 1), medulloblastoma (n = 2), ependymoma (n = 2), and pilocytic astrocytoma (n = 1). One patient with trigeminal neuralgia served as the normal control subject. No complications because of the stimulation sucker were encountered. Clinical and radiologic outcomes compared favorably with institutional experience and literature. The stimulation sucker allowed for continuous (time) mapping of the facial nerve at the site of resection (space). This real-time feedback allowed early identification of the facial nerve. Handling and ergonomy were excellent and workflow improved. The shortcomings compared with a bayonet-shaped bipolar probe were decreased visibility of neurovascular structures and lower spatial discrimination. The new device did not simplify delicate at the brainstem and on the nerve. We think it should be considered as a complementary tool in the surgeon's armamentarium. CONCLUSIONS: Until now, nerve damage as assessed by neuromonitoring (e.g., facial nerve electromyography, motor evoked potential) served as surrogate for nerve function. This concept should be challenged. The studied stimulation sucker detected the facial nerve earlier than conventional techniques, preventing harm by surgical trauma. A larger, prospective study is warranted to better define its role in CPA surgery.

Unusual exophytic subependymoma in the bulbo-cerebellar angle. Case report.

Subependymoma was first described by Scheinker in 1945; it frequently occurs in the ventricles and rarely in the spinal canal representing 0.7% of all central nervous system tumours. Most of these intraventricular tumours are subclinical entities, remaining of small size and discovered at autopsy with 0.4%incidence. We report a case of subependymoma with a completely exophytic growth from the foramen of Luscka: only a similar one has been described in the literature but with a lesser cysternal involvement. Neuroradiological and anatomopathological features of subependymoma are discussed.

Meningioma in the posterior fossa without dural attachment.

A 14-year-old boy presented with a very rare meningioma in the posterior cranial fossa without dural attachment. Magnetic resonance imaging revealed a 3-cm, well-circumscribed, heterogeneously enhanced, round mass without dural tail sign in the right side of the posterior fossa. Right vertebral angiography revealed very faint tumor staining supplied by the right posterior inferior cerebellar artery. Total removal of the tumor was performed. Intraoperatively, the mass exhibited no attachment to the dura mater, cerebellar parenchyma, or choroid plexus, but was firmly attached to the arachnoid tissue near the foramen of Luschka. Histological and immunohistochemical studies established the diagnosis of meningothelial meningioma (World Health Organization grade I).

Failure of fixation suppression of caloric nystagmus and ocular motor abnormalities.

Caloric nystagmus is substantially suppressed by visual fixation. The degree of suppression of caloric nystagmus is influenced by the condition of visual fixation. We studied the percent reduction in slow-phase velocity of caloric nystagmus by visual fixation and certain abnormalities in optokinetic nystagmus, smooth pursuit, and maintenance of ocular position of gaze in 38 patients with disorders of the CNS. The inability to suppress caloric nystagmus by visual fixation correlated with reduction in optokinetic nystagmus, deficit in smooth pursuit eye movements, and presence of gaze nystagmus. It seems probable that modulation of the vestibulo-ocular reflex is influenced by the same mechanisms that are concerned with optokinetic nystagmus, maintenance of ocular position of gaze, and smooth pursuit eye movements.

The EEG in deep midline lesions.

We studied the electroencephalograms (EEGs) of 154 patients with well-defined diencephalic, mesencephalic, or posterior fossa lesions. Electrographic and clinical parameters were statistically evaluated. The results indicated considerable overlap of EEG abnormalities from different subcortical sites. Focal or lateralized abnormalities were relatively specific, suggesting a diencephalic lesion, whereas bilateral paroxysmal slow-wave disturbances were unspecific and not of precise diagnostic significance. There was no specific feature in this series to clearly distinguish the EEG pattern in deep midline lesions from that seen with diffuse cortical and subcortical encephalopathies.

Nausea as a complication of low-frequency repetitive transcranial magnetic stimulation of the posterior fossa.

BACKGROUND: Transcranial magnetic stimulation (TMS) can non-invasively investigate the function of human brain. However, it can induce a focal pain at the stimulated site on the scalp or seizures when applied with high frequency (>1 Hz). Here we report an induction of nausea as a complication of low-frequency repetitive TMS (rTMS) of the cerebellum. SUBJECTS AND METHODS: Eight right-handed normal volunteers underwent low-frequency (0.9 Hz) rTMS of the right cerebellum. The stimulus intensity was set at 90% of the resting motor threshold determined by TMS to motor cortex. RESULTS: Nausea lasted as long as 10 min after the end of rTMS without apparent neurological deficit in two subjects. This symptom was replicated when the same protocol was applied on a different day in the same subjects. CONCLUSIONS: Low-frequency rTMS of cerebellum is still a safe procedure, but the experimenters should keep in mind the possibility of inducing nausea.

Late onset cerebello-pontomesencephalic degeneration.

Two siblings are presented with late onset, rapidly progressive truncal ataxia, paralysis of down-gaze and loss of up-gaze saccades in association with other oculomotor dysfunctions as well as dementia. Electron microscopic muscle studies revealed abnormal distribution and form of the mitochondria, probably being the ultrastructural basis of the pathologic changes. A neurological syndrome as that described here has not been reported before.

The differential diagnosis of cerebello-pontine angle lesions. A multidisciplinary approach with special emphasis on the brainstem auditory evoked potential.

92 patients thought to have a cerebello-pontine angle tumour on initial presentation were studied prospectively using standard neuro-otological techniques, brainstem evoked potential recording with a variety of montages, middle latency auditory evoked potentials and CT scanning. 64 patients had a tumour, 40 of which were acoustic neuromas. By analysing the data from all disciplines it has been possible to delineate clusters of variables that are of value in the differential diagnosis of cerebello-pontine angle lesions.

Orthodromic (intra/extracranial) neurography to monitor facial nerve function intraoperatively.

This report introduces the technique of orthodromic neurography for monitoring of facial nerve function during operation in the cerebellopontine angle. By stimulation of the intracisternal segment of the facial nerve, a compound nerve action potential with amplitudes of 15 to 480 microV can be recorded extracranially from the nerve near the stylomastoid foramen after 0.95 to 2.27 ms. Usually there is no need for signal averaging, and the method is independent of the effect of muscle relaxants. With the use of the same electrophysiological equipment as for evoked potential neuromonitoring, immediate and repeated localization of the facial nerve and its discrimination from the trigeminal and the lower cranial nerves during nerve preparation within the tumor capsule is possible.

Changes in contralateral brain-stem auditory evoked responses to cerebellopontine angle compression in rats.

Eleven rats were subjected to graded compression of the brain stem at the cerebellopontine angle (CPA) following craniectomy and cerebellectomy. Clicks were delivered to the ear contralateral to the compression site, and brain-stem auditory evoked responses (BAER's) were collected before and during compression. With increasing compression, there was an increase in the latency and a decrease in the amplitude of the peaks of the BAER. The later peaks of the BAER (V and VI) demonstrated changes with minimal compression that progressed as compression increased, while changes in the amplitude and latency of the earlier peaks (II, III, and IV) occurred at the higher grades of compression. Following decompression of the brain stem, there was a decrease in the latencies of most of the BAER peaks. Peak amplitude remained depressed following brain-stem decompression. These experimental findings corroborate clinical reports of abnormal BAER's elicited from stimulation of the ear contralateral to a CPA tumor. The relative sensitivity of the later peaks of the BAER to even minimal brain-stem compression explains the prolonged III to V interpeak latency reported in the literature in patients with brain-stem compression from a CPA lesion. The possible mechanisms for the BAER changes that were observed contralateral to compression are discussed.

Hearing preservation in acoustic neuroma surgery: a continuing study.

Hearing preservation in acoustic neuroma surgery is possible in a limited number of cases. Although there have been many articles published about hearing preservation, there have been few studies of long-term hearing results, nor is it known if there is an increased rate of tumor recurrence when hearing preservation is attempted. Twenty-two patients who underwent a hearing preservation procedure via the retrosigmoid approach were selected from 80 consecutive patients with cerebellopontine angle tumors operated on from February 1984 to November 1987. Useful hearing was retained in 11 cases as reported in a previously published study. Seven patients continue to have useful hearing after 3 to 5 years; 3 have shown a gradual but slight decline. There has been no tumor recurrence in these patients, but 2 patients, operated on early in the series and who had lost hearing, had recurrent tumor.

Cochlear nerve monitoring during cerebellopontine angle operations.

The authors present their experience with intraoperative monitoring of cochlear nerve action potentials (AP) in 30 adult patients. Operative procedures were acoustic neuroma excision with attempted hearing preservation and selective vestibular neurectomy in patients with incapacitating Meniere's disease and serviceable hearing (SRT less than 50 db, discrimination greater than 60%). Loss of AP is detected rapidly and has been demonstrated after manipulation of the cochlear nerve and after coagulation of small arteries on the tumour capsule. Presence of an AP at the end of the procedure usually correlates with postoperative preservation of hearing. AP monitoring appears to be a reliable means of detecting potentially reversible changes in cochlear nerve function intraoperatively.

Brainstem response in cerebellopontine angle tumors.

OBJECTIVE: To evaluate the auditory brainstem response (ABR) findings in cerebellopontine angle (CPA) tumors and focus on those with normal ABR results. STUDY DESIGN: This was a retrospective evaluation of ABR findings. All subjects with diagnosed CPA tumors who were referred for treatment were included. PATIENTS: All 309 patients with radiographically confirmed (computed tomography or magnetic resonance imaging [MRI]) CPA tumors (153 before 1993 and 156 after 1993). INTERVENTION: All patients underwent complete audiologic examination, electronystagmography, ABR testing, and ipsilateral transtympanic electrocochleography. All tumors were histologically confirmed. MAIN OUTCOME MEASURES: The patients were categorized according to ABR results (normal or pathologic findings or no response); according to histology (vestibular schwannomas or meningiomas); and according to tumor size by MRI (small, up to 15 mm; medium, 16-25 mm; large, 26-40 mm; and very large, over 40 mm). RESULTS: Normal ABR results were found in 18.4%; pathologic ABR results in 31.4%; and no response in 50.2%. Small vestibular schwannomas (under 15 mm) showed a higher incidence of normal ABR results (41.7%). CPA tumors with normal ABR results (n = 57) caused no hearing loss (n = 12), symmetrical hearing loss (n = 11), or ipsilateral hearing loss with Short Increment Sensitivity Index 100% and normal acoustic reflex (cochlear deafness, n = 34). Caloric response was normal in 59.7% of these tumors. CONCLUSION: Because validation of ABR as screening for acoustic tumors is based on diagnosed tumors, and because MRI allows detection of very small tumors, the incidence of normal ABR increases and its sensitivity would be expected to decrease. ABR is not sufficient for early detection of small CPA tumors.