Introduction

Neurofibromatosis type II (syn Acoustic neurofibromatosis, Bilateral vestibular schwannoma disease, Gardner type neurofibroma, Wishart type neurofibroma) is classified under the phakomatoses though cutaneous manifestations are uncommon in the type II subgroup.^[1,2]

It is an autosomal dominant type of inherited disorder showing no racial or sexual predominance. The hallmark of the syndrome is multiple schwannomas – the most typical site being the VIII cranial nerve.

Previously called the central type of neurofibromatosis (as opposed to NF-I – the peripheral type), such distinctions are now considered obsolete as NF-II has peripheral manifestations and vice versa.

Case Report

A 25 years old female patient presented with seizures and long term history of hearing loss and upper backache. Physical examination was unremarkable. Audiometry revealed bilateral sensorineural type of hearing loss.

Figure 1

Figure 1: Radiograph of skull (lateral view) shows multiple radio opacities (arrows) on lateral Projection (fig 1).

Plain and contrast C.T. study of brain performed on GE Healthcare 16-slice scanner showed two enhancing structures at the cerebello-pontine angle extending into the internal acoustic meatus through the Porus Acousticus with extra-axial rounded enhancing lesions in the falx and over the cerebral convexities with underlying bony hyperosteosis (fig 2).

Figure 2

Figure 2: Brain axial contrast C.T. scan shows multiple enhancing lesions (thin arrow) in falx and cerebral convexities with bony hyperosteosis(thick arrow)

MRI study of the brain and spine performed on 1.5T Siemens Magnetom Essenza machine which included T2 weighted axial sequences and 3D contrast enhanced T1 sequences showed enhancing extra-axial mass lesion at the cerebello-pontine angle extending into the internal auditory canal with displacement of the brainstem producing compression effect over the 4th ventricle (fig 3).

Figure 3

Figure 3 : MRI brain (T1 axial post-contrast) shows enhancing extra-axial lesions at cerebello-pontine angle (arrows).

T2 weighted sagittal study of spine showed intra-dural extra-medullary mass lesion dorsal to the thoracic part of spinal cord, pushing it anteriorly (fig 4)

Figure 4

Figure 4 : T2W sagittal scan of spine showing intra-dural extra-medullary mass lesion, dorsal to the thoracic spinal cord (arrow)

Presumptive diagnosis of NF-II was considered after applying National Institute of Health consensus criteria for NF-II.

Discussion

One of the rarer varieties of phakomatoses, NF II has an incidence of about 1 in 30 to 40 thousand and a prevalence of about 1 in 2,10,000. Inherited as an autosomal dominant disease, the genetic defect has been identified as deletions from chromosome 22. Persons with this abnormal chromosome 22 are predisposed to schwannoma, meningiomas, ependymomas, intracranial non-tumoral calcification.^[2,3,4]

Cutaneous manifestations like neurofibromas and schwannomas are uncommon in NF-II as compared to NF-I and they rarely have café-au-lait spots.

Most classical site of schwannoma associated with this syndrome is the VIIIth cranial nerve, followed by the Vth cranial nerve.

Mostly presenting in the 2^nd to 3^rd decade, the typical clinical features are related to symptoms related to the effects of an intracranial SOL and the disturbed anatomy of the VIIIth cranial nerve - like hearing loss, imbalance and seizures.^[5] In females, an exacerbation in the clinical severity is noted during pregnancy.^[6] The vestibular schwannomas associated with this are invasive (as opposed to sporadic vestibular schwawnnomas).^[7,8]

Patients of NF-II may also show ocular pathologies in the form of early onset juvenile posterior sub-capsular cataract[9,10,11,12,13], retinal and choroidal hamartomas, optic nerve sheath meningiomas all of which may also affect patient’s vision.

National Institute Of Health Consensus Criteria For NF-II

Definite diagnosis of NF2

Presumptive diagnosis of NFII