Acoustic neuroma is a benign tumor of the eighth cranial nerve. The document discusses the definition, histopathology, etiology, classification, clinical features, investigations, differential diagnosis, and management of acoustic neuroma. The key signs and symptoms include progressive hearing loss, tinnitzus, imbalance, and cranial nerve involvement including facial numbness. MRI with gadolinium is the gold standard for diagnosis. Treatment options include surgical removal via middle cranial fossa, translabyrinthine, or suboccipital approaches or stereotactic radiotherapy using gamma knife or cyber knife.
6. Origin & Growth
• Origin:
Schwann Cells of Vestibular Nerve, rarely from
cochlear nerve
• Growth: (slow)
Causes widening and erosion of the canal and
appears in the CP angle
Anterosuperior growth: 5th
Inferior: 9th , 10th & 11th
Later stages: displacement of brainstem, pressure on
cerebellum and raised intracranial tension
9. Clinical Features
• Age : 40-60 years
• Sex: M=F
• Symptoms:
1. Progressive unilateral SNHL
2. Tinnitus
3. Marked difficulty in understanding speech
4. Imbalance/ Unsteadiness
5. Vertigo
6. Sudden Hearing loss
7. Fullness in the ear
10. Cranial Nerve Involvement
1. 5th nerve: EARLIEST
Reduced cornea sensitivity, paraesthesia of face
Involvement indicates : tumour size = 2.5cm &
occupies CP angle
2. 9th & 10th : dysphagia & hoarseness due to
palatal, pharyngeal, laryngeal paralysis
3. Other cranial nerves: affected only when tumour
size is very large
11. Cranial Nerve Involvement
Facial nerve:
• Sensory fibres are affected early.
• Hitzelberger’s sign : Hypoaesthesia of
posterior meatal wall
• Loss of taste ( Electrogustometry)
• Schirmer test : Reduced lacrimation
• Motor fibres: Affected late
• Delayed blink reflex
12. Brainstem Involvement
• Ataxia
• Weakness & Numbness of arms
and legs
• Exaggerated tendon reflexes
Raised Intra-cranial tension
Headache, nausea, vomiting, diplopia(6th) &
papillo-edema with blurring of vision.
13. Cerebellar involvement
• Pressure symptoms on cerebellum are seen in
large tumors
• Revealed by
Finger-nose test
Knee-heel test
Dysdiadochokinesia
Ataxic gait
Inability to walk along a straight line (tendency to
fall on the affected side)
14. Investigations
• Audiological tests:
1. PTA
2. Speech Audiometry
3. Recruitment
phenomena: Absent
4. Short Increment
Sensitivity Index: 0-20%
5. Threshold tone decay
test : Retrocochlear type
of lesion
15. Vestibular Tests
• Caloric test:
Diminished or absent
response in 96% of
patients
May be normal when
tumour is small
17. Radiological tests
1. Plain X-ray:
• Positive in 80% of patients
• Different views:
1. Transorbital
2. Stenver’s
3. Towne’s
4. Submentovertical
2. Vertebral angiography:
• Helps in differentiating AN from other tumours
18. Radiological Test
3. CT scan:
• More sensitive than X-ray
• Can detect even intra-meatal and
posterior fossa tumors
4. MRI with Gadolinium contrast:
• GOLD Standard
• Can detect even intracanalicular
tumours of few mm
20. Other tests
• BERA:
A delay of >0.2ms in
wave V between 2 ears in
case of 8th nerve tumour
• CSF Examination:
Protie level raised, Lumbar
puncture should be
avoided
21. Investigations
Important tests for AN work-up:
• PTA
• Speech discrimination score
• Roll-over curve
• Stapedial reflex decay
• BERA
• MRI with gadolinium contrast
22. Differential Diagnosis
• Meniere’s Disease
• Tumours of CPangle:
1. Meningioma
2. Epidermoid
3. Arachnoid Cyst
4. Schwannoma of other cranial nerves
5. Aneurysm
6. Glomus tumour
7. Metastasis
26. X-knife/ɣ-knife surgery
• Stereotactic radiotherapy
• Advantages:
1. Minimal radiological effect
2. Causes reduction in tumour size &
growth.
3. Can be used in patients where surgery is
not feasible.
• Procedure : linear accelerator
ɣ-knife through cobalt-60
27. Radiotherapy
Conventional:
• Not prefered now due to low
tolerance of CNS to radiation
Cyber knife:
• Modified X-knife
• More accurate & frameless
• Method: real-time image
guidance technology through
computer controlled robotics.
