A rare case of recurrent Vestibular Schwannoma

Introduction

Vestibular Schwannoma (VS) or acoustic neuroma constitutes 80% of all cerebellopontine angle tumours and 10% of all the brain tumours. It is a benign, encapsulated, extremely slow growing tumour of the VIII nerve. The tumour almost always arises from the Schwann cells of the vestibular division of the VIII cranial nerve, but rarely from the cochlear division of VIII nerve within the internal auditory canal1. As it expands, it causes erosion of the canal and then it appears in the cerebellopontine angle. Here, it may grow antero-superiorly to involve V, and/or VII nerve or inferiorly to involve IX, X, or XI cranial nerves. In later stages, it causes displacement of brainstem, pressure on cerebellum and raised intracranial tension1. The recurrence rate after excision is less than 5%. Facial nerve paralysis appears to occur in about 15-30% of patients but most make a complete recovery over time. Hearing loss occurs in more than 50% of patients and may not improve over time. Residual hearing loss has a significant impact on the quality of life.^2-4

Case Report

A 60-years old female came to the Medicine OPD with complaints of vertigo, dysarthria, nasal regurgitation, hearing loss in right ear and swaying to right side while walking since 20 days. There was a past history of right sidevestibular Schwannoma for which she was operated 3 years ago and remained symptom free after operation. There was no history of weakness of limbs, fever, vomiting and headache. There was no past history of cerebrovascular accident, hypertension and diabetes mellitus. There was no significant family history.

On clinical examination of the central nervous system, there was deviation of the angle of the mouth to the right side, weakness of right buccinator muscle, decreased nasolabial fold on right side and corneal sensation in right eye was reduced. There was right ear sensor neural hearing loss and gag reflex was reduced. The uvula was deviated to the right side, and there wasdeviation of the tongue to the right side. Motor and sensory system examination was normal. Cerebellar system examination revealed inco-ordination in both right upper and lower limbs. Systemic examination of abdomen, respiratory and cardiovascular system showed no abnormalities.

Routine blood investigations were normal. MRI Brain showed right cerebello-pontine angle neoplastic mass with compression on brain-stem causing proximal hydrocephalus, altered signal intensities in right cerebellar hemisphere and craniotomy defect. The impression on MRI was vestibular Schwannoma.

Discussion

Vestibular Schwannoma are common benign neoplasia and constitute 8-10% of all intracranial tumors5. Incidence has been estimated about 1 new case per 100,000 population per year⁶, although histologic studies from autopsies had reported that micro tumours are present in 2% of individuals⁷.Vestibular Schwannoma arises from Schwann cells of the vestibular nerves, usually at the IAC. Tumour growth is slow, and usually they extend to the cerebellopontine angle. Lateral extension to the labyrinth is relatively common, but progression to the middle ear is rare. Some authors have reported extension of vestibular Schwannomas to the middle ear, but most of them were possibly originated into the labyrinth.^8-11

Taking into account that reported isolated intralabyrinthine schwannomas do not extend to the cerebellopontine angle,^8-11 they probably arise at the fundus of the IAC. There are several surgical approaches to schwannomas removal. By far the most used are the trans-labyrinthine and the sub occipital retro sigmoid approaches. 12 In cases of large tumors with extension to the petrous bone, the transotic approach gives a convenient exposure. The major disadvantage of this approach is the increased risk of facial lesion after the nerve translocation¹³.

The present case points the possibility of schwannomarecurrence. A careful preoperative study of extension is mandatory, particularly when a non-trans-labyrinthine approach is used (due to ignored labyrinthine involvement). The rate of VS recurrence after total removal is exceptionally low in experienced hands. Undetected microscopic deposits left on crucial points such as the facial nerve, the preserved cochlea nerve, or the fundus of the internal auditory canal could be possible causes for the recurrence. A definite advantage of an ETL approach is the excellent internal auditory canal exposure, resulting in an extremely low rate of VS recurrence.14 The patients should be followed up to 15 years with gadoliniumenhanced magnetic resonance imaging (with fat suppression sequence in ETL approach cases). Recurrent VS may exhibit a faster growth rate than primary VS. Thus, despite the approach used, an adequate follow-up is necessary to detect and treat asymptomatic recurrences.¹⁴

Conclusion

Acoustic neuromas are not common tumours in clinical practice. However, they often present with unilateral hearing loss and thus healthcare workers should consider the lesion in the differential diagnosis of patients presenting with unilateral hearing loss and vertigo. The tumour once diagnosed is best managed by a multidisciplinary team that includes a neurosurgeon, neurologist, ENT surgeon, and a hearing specialist. As recurrence rate is 5% it requires regular monitoring of the patient.