Prospective observational study for the evaluation of clinical and radiological correlates in patients undergoing surgery for vestibular schwannoma
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Date
2019-12
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SCTIMST
Abstract
Cerebellopontine angle (CPA) tumours comprise 5 to 10 percent of all intracranial
tumours. Around 90 % of all CPA tumours are vestibular schwannomas, which are
benign tumours of the vestibular portion of the vestibulocochlear nerve, arising from the
Schwann cells. They first originate in the intracanalicular part of the nerve and grow
slowly out into the cisterns. They present with unilateral sensorineural hearing loss with
poor speech discrimination (77 to 95 %), unilateral non pulsatile tinnitus (53 to 70%),
vestibular dysfunction, trigeminal nerve symptoms, cerebellar dysfunction, headache,
facial nerve dysfunction, raised intracranial pressure and lower cranial palsy. Long tract
signs are a late finding in patients with vestibular schwannomas and these have become
extremely rare in modern series. (1,2)
Long tract involvement may present with hyperactivity of ipsilateral deep tendon
reflexes, increased tone of the musculature and Babinski sign - extensor plantar response.
Rarely extremity weakness and ipsilateral sensory symptoms are found in a small subset
of patients. (1 - 10)
Diffusion tensor imaging of the brainstem allows delineation of the white matter tracts of
the brainstem. It allows subjective quantification of the directional diffusion of the water
in the white matter tracts. Lui et al found that in circumscribed posterior fossa primary
lesions there was a correlation between clinical weakness and higher mean diffusivity,
lower fractional anisotropy and lower transverse eigenvalue values. (55)This study can assess the subset of the patients with vestibular schwannomas who present
with long tract signs and their correlation with tractography findings preoperatively. The
intraoperative nature of the tumour and the histopathological characteristics will be noted
and the postoperative outcome with repeat imaging will be assessed. Through this study,
we objectively hope to define the less commonly studied manifestation of vestibular
schwannomas, the long tract signs - the size of the tumour beyond which they tend to
occur - both clinically and radiologically. There is scarcity of research correlating clinical
data with DTI imaging findings and the post operative follow up data, showing outcome
after resection. This study hopes to assess the utility of diffusion tensor imaging to
objectively quantify the involvement of long tracts in vestibular schwannomas and its
usefulness in predicting post operative outcome. The Principal Investigator of this study
regularly operates on vestibular schwannomas and we hope that this data will add on to
the understanding of the long tract involvement in vestibular schwannomas.