This powerpoint presentation explains Acoustic Neuroma in simple words. For further reading, please refer standard textbooks of Otorhinolaryngology.

1. ACOUSTIC NEUROMA
Saikiran M
Roll No 171
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2. Contents
◦ Introduction
◦ Pathology and Classification
◦ Clinical Features
◦ Investigations and Diagnosis
◦ Differential Diagnosis
◦ Treatment
◦ Complications and Prognosis

3. Introduction
◦ Acoustic neuroma is a benign, encapsulated, extrememly slow growing tumor of
VIIIth
cranial nerve.
◦ Acoustic neuroma is also known as vestibular schwannoma, neurilemma or eight
nerve tumour.
◦ It is seen in 80% of all cerebellopontine angle tumours and 10% of all brain
tumours.
◦ It has got high association with Neurofibromatosis Type 2 (NF2), an autosomal
dominant condition.

5. Pathology
◦ Microscopically, it consists of elongated spindle cells with rod shaped nuclei lying
in rows or palisades.
◦ Neurofibromatosis patients may have bilateral tumours.
◦ It arises from the schwann cells of vestibular part of VIIIth
nerve within the
auditory canal.
◦ As it grows and erodes the canal it appears in the cerebellopontine angke to
grow anterosuperiorly or inferiorly to affect the other nerves (Vth, VIIth, IXth,
Xth, XIth).
◦ In later stages, it can displace the brainstem, put pressure on cerebellum and
raised intracranial tension.

7. Classification
◦ Depending on its size, the tumour is classified as:
◦ Intracanalicular
◦ Small size (upto 1.5cm)
◦ Medium size (upto 1.5-4cm)
◦ Large size (over 4cm)

8. Clinical Features
1. Age and Sex : mostly seen in 40-60 years of age and both sexes are equally
affected.
2. Cochleovestibular symptoms: Progressive unilateral sensorineural hearing
loss often with tinnitus is the presenting symptom in majority of cases.
3. Cranial nerve involvement:
◦ Vth nerve: There will be reduced corneal sensitivity, numbness or paresthesia of face.
This shows that the tumour is roughly 2.5 cm in diameter and occupies the
cerebellopontine angle.
◦ VIIth nerve: Sensory fibres affected. Hypoaesthesia of posterior meatal wall, loss of
taste and reduced lacrimation on Schirmer test. Motor fibres are affected late and may
cause delayed blink reflex.

9. ◦ IXth and Xth nerves: There is dysphagia and hoarseness due to palatal,
pharyngeal and laryngeal paralysis.
1. Brainstem involvement: Ataxia, weakness and numbness of the arms and
legs with exaggerated tendon reflexes.
2. Cerebellar involvement: Finger-nose test, knee- heel test,
dysdiadochokinesia, ataxic gait and inability to walk in a straight line with
tendency to fall to affected side.
3. Raised intracranial tension: headache, nausea, vomiting, diplopia due to VIth
nerve involvement and papilledema with blurring of vision.

10. Investigations and diagnosis
1. Audiological tests :
◦ Pure tone audiometry- sensorineural hearing loss (more marked in higher frequencies).
◦ Speech audiometry- poor speech discrimination. Roll-over phenomenon is observed.
◦ Recruitment phenomenon is absent.
◦ Short Increment Sensitivity Index test will show a score of 0-20% in 70-90% cases.
◦ Threshold tone decay test- retro-cochlear type of lesion.
2. Stapedial Reflex Decay Test:
3. Vestibular tests: Caloric test will show diminished or absent response in 96%.
4. Neurological tests: Complete CNS examination is done + Fundus is examined
for blurring of disc margins or papilledema.

12. 1. Radiological tests:
a) Plain X- rays: Transorbital, Stenver’s, Towne’s and submentovertical views give positive
findings in 80% cases
b) CT scan: Small tumours can be detected, if combined with intrathecal air, an intrameatal
tumour can also be recognised
c) MRI with gadolinium contrast: This is gold standard for diagnosis. Intracanalicular tumours
of even millimetres can be identified.
d) Vertebral angiography: Helps to differentiate acoustic neuroma from other tumours of CPA.
2. Brainstem Evoked Response Audiometry: Used to diagnose retro-cochlear lesions.
3. CSF examination: Protein levels are raised.

14. Differential Diagnosis
1. Meniere’s disease: Episodic vertigo with fluctuating hearing loss, tinnitus but
imaging is normal.
2. Sudden sensorineural hearing loss (idiopathic): Rapid onset, no vestibular
schwannoma on imaging.
3. Other CPA lesions: Meningioma, cholesteatoma, schwannoma of other cranial
nerves, glomus tumour.

15. Treatment
1. Observation:
a) Indicated for small, asymptomatic or very slow growing tumours, especially in older
or comorbid patients.
b) Periodic MRI and audiometric evaluations to monitor growth.
2. Surgery: It is the treatment of choice. A surgical approach would depend on
the size of the tumour. The various approaches are:
a) Middle cranial fossa approach
b) Translabyrinthine approach
c) Suboccipital (retrosigmoid) approach
d) Combined Translabyrinthine- suboccipital approach

17. 1. Radiotherapy:
a) X-knife or Gamma knife surgery: A form of stereotactic radiotherapy. The
surrounding tissue is spared. Causes arrest of growth of tumour and also reduces its
size. X-knife surgery is done through linear accelerator and gamma-knife through
a Cobalt 60 source.
b) Cyber knife: It is an improvement over the above and is totally frameless and more
accurate. It uses real-time image guidance technology through computer controlled
robotics.

19. Complications and Prognosis
1. Complications:
a) Postoperative Facial Nerve Palsy
b) CSF Leak
c) Residual/ Recurrent Tumour
2. Prognosis:
a) Generally good for small tumours, detected early.
b) Even for larger tumours, surgical and radiotherapeutic advances have improved
outcomes.
c) Preservation of facial nerve function is a crucial measure of success.