Download 1912 Acoustic Neuroma Surgery

Case presentation and brief review of acoustic
neuroma
Dr. (Col). G. Vyas, ***, Dr. S. Vaidya ***, Dr. Ashish Sharma**
Case History
A 55year old male nonsmoker, non alcoholic, non hypertensive, non diabetic,
stenotypist by occupation presented with complaints of unilateral hearing loss
right ear, tinnitus for last three years. There is no history of headache, trauma,
convulsions, projectile vomiting. There is no history of Tuberculosis, diabetes
mellitus, hypertension or any other chronic illness in past.
He had been previously diagnosed and treated as case of cardiomyopathy.
For the complaints of hearing loss in right ear, tinnitus for last three years, he
had been consulted by various ENT consultants and was subjected to all relevant
investigations including audiometery which revealed unilateral deafness.
On 3 April when he was returning from his office work he lost consciousness
which lasted for almost 10 minutes after that he regained consciousness. There
was no neurological deficit at that time except sustained injury on left side due to
fall.
He was subjected to all routine investigations and MRI. Report of all routine
investigations were found to be in normal limits.
MRI revealed acoustic neuroma with intra canalicular extension.
Due to his medical condition he was advised Gamma Knife Radiosurgery as
primary treatment option to achieve tumor control and preserve facial nerve
function.
Patient was shifted to Gamma Knife Suite and Leksell stereotactic head frame
was applied under sedation in supine position. The skull measurements were
recorded and imaging of head [stereotactic MRI] was obtained. The radiological
images were then network transferred to Gamma Plan and treatment planning
was performed. Total five shots were delivered using two 18 mm collimator
shots, and three 8 mm collimator shots. 100% of tumor volume [4.1 cubic cms]
was delivered prescription dose > =12.0 Gy at 50% prescription isodose
configuration. Maximum dose to the tumor was 24.0 Gy. Patient tolerated the
procedure well.
** Associate Professor, *** Professor & Head Department of Medicine,
***Associate Professor Department of ENT, R.D. Gardi Medical College, Ujjain.
MRI IMAGES OF PATIENT
Gamma Knife Snapshot
REVIEW OF ACOUSTIC NEUROMA
Historical Perspectives
1905
Harvey Cushing, did surgery of acoustic neuroma, Meticulous
dissection, Hemostasis: silver clips, bone wax, electrocautery, Mortality:
rate with this strategy reduced from 20 % (1917)  4% (1931)
•
1916 Dr. Walter Dandy, Complete removal of AN, Mortality: 10%,
•
Early 1960s Dr. William House used, Translabyrinthine approach using
surgical drill and operating microscope
Epidemiology
• 6 % of all Intracranial tumors, 80 - 90% of CPA tumors
• Incidence in US: 10 per million / year
• Vast majority in adulthood, No known race, gender predilection
• 95% Sporadic (unilateral), 5% Neurofibromatosis type 2 (bilateral)
Pathogenesis
• Schwannoma arising from vestibular nerve
• Benign tumor,. Malignant degeneration exceedingly rare.
• Majority originate within the IAC, Equally frequent on Superior and Inferior
vestibular nerves.
Jackler Staging System is used to stage acoustic neuroma as per size and
extension of tumor.
Stage
Intracanalicular
Tumor Size
Tumor confined to IAC
I (small)
II (medium)
III (Large)
< 10 mm
11-25 mm
25-40 mm
IV (Giant)
> 40 mm
Phases of Tumor Growth
• Intracanalicular:
– In this phase Hearing loss, tinnitus, vertigo are more common
• Cisternal:
– Worsened hearing and dysequilibrium
• Compressive:
–
•
In compressive phase, Occasional occipital headache and
involvement of 5th CN leading to Hypesthesia of cornea and
Midface
Hydrocephalic:
– Fourth ventricle compressed and obstructed causing, Headache,
visual changes, altered mental status
Phases of Tumor Growth
Intracanalicular
Compressive
Cisternal
Hydrocephalic
Hearing Loss is the most frequent initial and common symptom occurring 95 % of
AN patients. It is asymmetric SNHL, Down-sloping and High Frequency with
decreased speech discrimination.
Pathophysiology of Hearing Loss in Acoustic Neuroma, Exact etiology is
unknown
•
Probable mechanisms are Compressive effect on cochlear nerve.
Vascular occlusion of internal auditory artery, Biochemical alterations
inner ear fluids
•
There is Lack of conclusive correlation between tumor size and
hearing
Estimating Tumor Growth
•
Serial MRI with and without GAD is the only reliable study to estimate
tumor growth rate
Diagnosis
History and Physical examination
Symptoms
• Hearing Loss
• Vertigo
• Dysequilibrium
• Tinnitus
• Headache
• Nystagmus
– Early small lesion: Horizontal (vestibular)
– Late large: Vertical (brainstem compression)
• Cranial neuropathy
– CN V, VII
– Lower cranial nerves (IX-XII)
Frequency of Symptoms
• Hearing Loss (85-97% ; 94% ) Vertigo (5-70 % ; 39% )
• Dysequilibrium (46-70% ; 56 %) Tinnitus (56-70% ; 64 %)
• Facial nerve (10-77% ; 38 %) Trigeminal nerve
(16-63% ; 26 %)
• Headache (12-38% ; 25% ) Visual symptoms (1- 15 % ; 7% )
• Lower cranial nerves: Dysphagia, Hoarseness, Aspiration, Shoulder
weakness (Jugular foramen syndrome)
Acoustic neuroma may present with Sudden Sensorineural Hearing loss,
the cause of which is Idiopathic,1-2 % SSNHL patients have AN, 10- 26 % AN
patients have a history of SSNHL Most experts advocate obtaining MRI in all
patients who present with SSNHL
Diagnosis
• History and Physical Exam
• Audiology testing:
– Audiogram
– ABR
– OAE
• Vestibular testings (eg. ENG, rotary chair, posturography) all lack
diagnostic value
• Radiography
– MRI is the gold Standard
– CT Scan
ABR: Diagnostic Efficiency, Generally, Efficiency increases with Size with the
Sensitivity: of > 90 % for tumor > 3 cm, No response for severe/ profound SNHL
IT5 and tumor size by auditory brainsten response interaural latency difference
for wave V (IT5)
OAE
• Reflect cochlear/ OHC / sensory hearing, Not primarily used as screening
tool
• Presence of OAE in SNHL ↔ Retrocochlear
• However, 50 % AN demonstrate both cochlear and retrocochlear hearing
loss
• Risk stratification for hearing preservation surgery
MRI Brain w. & w/o GAD Gold standard investigation for diagnosis of
acoustic neuroma
T1 pre-Gad
•
•
•
T1:
T2:
T1+Gad:
T2
T1 post-Gad
Isointense to brain, hyperintense to CSF
Hyperintense to brain, hypointense to CSF
Enhancing
CT Brain with contrast
Heterogeneous enhancement on contrast with Rarely calcification
It is the investigation of choice where MRI is Contraindicated (metallic implants),
claustrophobic patients
CT Scan May not be able to detect small tumor < 1.5cm
Treatment options are
•
•
•
Observation
Surgery by any of these approach
– Translabyrinthine
– Retrosigmoid
– Middle fossa
Radiotherapy
– Conventional
– Stereotactic
– Gamma knife ablation
Conservative Management is indicated in the following conditions
• Advanced age (> 65 ), Short life expectancy (< 10 years), Slow growth
rate
Poor surgical candidate / poor general health, Minimal symptoms
Only hearing ear and Patients preference
Conclusions
• Tumor size has no correlation with audiovestibular symptoms in
Acoustic neuroma, Understanding tumor growth rate is important for
predicting symptom progression and treatment planning and the
study-of-choice to estimate tumor growth is serial MRI
References:
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