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

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Gamma Knife Snapshot

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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 |Tumor Size |

|Intracanalicular |Tumor confined to IAC |

|I (small) |< 10 mm |

|II (medium) |11-25 mm |

|III (Large) |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

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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

[pic]

• T1: Isointense to brain, hyperintense to CSF

• T2: Hyperintense to brain, hypointense to CSF

• T1+Gad: 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

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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:

• NIH Consensus Statement Online 1991 Dec 11-13 ;9(4):1-24

• Baker R, Stevens-King A, Bhat N and Leong P (2003). "Should patients with asymmetrical noise-induced hearing loss be screened for vestibular schwannomas?" Clin Otolaryngol 28(4): 346-51.

• vestibular schwannoma resection. Laryngoscope 2003 Mar;113(3):420-6

• Daniels and others. Causes of unilateral sensorineural hearing loss screened by high-resolution fast spin echo magnetic resonance imaging: review of 1070 consecutive cases. Am. J. otol 21:173-180, 2000

• Evans, D. G., A. Moran, et al. (2005). "Incidence of vestibular schwannoma and neurofibromatosis 2 in the North West of England over a 10-year period: higher incidence than previously thought." Otol Neurotol26(1): 93-7.

• Falcioni M, Taibah A, Di Trapani G, Khrais T, Sanna M. Inner ear extension of vestibular schwannomas. Laryngoscope. 2003 Sep;113(9):1605-8.

• Hoistad DL and others. Update on conservative management of acoustic neuroma. Otol Neurotol 22:682-685, 2001

• House JW, Bassim MK, Schwartz M. false-positive magnetic resonance imaging in the diagnosis of vestibular schwannoma. Otology and Neurotology 29:1176-1178, 2008

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• Jackler RF. Diagnosing Acoustic Neuromas. Audio-Digest Otolaryngology 33, 04, Feb 21, 2000

• Jackler RF. Acoustic neuromas: selective managemetn Audio Digest Otolaryngology, April 7, 2007.

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• Levo H, Blomstedt G, Pyykko I. Postural stability after vestibular schwannoma surgery. Ann Otol Rhinol Laryngol 2004;113:994-9.

• LIMB CJ, Long DM, Niparko JK. Acoustic Neuromas after Failed Radiation Therapy: Challenges of Surgical Salvage. Laryngoscope 2005;115:93-98.

• Mayo clinical update. Volume 14, #2, 1998.

• Morrison GA, Sterkers JM. Unusual presentations of acoustic tumors. Clin Otolaryngol 1996, 21(1) 80-3.

• Nageris BI, Popovtzer A. Acoustic neuroma in patients with completely resolved sudden hearing loss. Ann Otol Rhinol Laryngol 2003 May;112(5):395-7

• Neff B, Willcox T, Sataloff R. Intralabyrinthine schwannomas. Otol Neurotol 24: 299-307, 2003

• Nikolopoulos TP, O'Donoghue Gm. Acoustic neuroma management: an evidence-based medicine approach. Otol Neurotol 23:534-41, 2002

• Perry BP, Gantz BJ, Rubinstein JT. Acoustic neuromas in the elderly. Otol Neurotol 22: 389-391, 2001

• Piazza F and others. Management of acoustic neuromas in the elderly: Retrospective study. ENT journal, May 2003, 374-378

• Sanna M and others. Treatment of residual vestibular schwannoma. Otol Neurotol 23:980-987, 2002

• Schaller B, Baumann A Headache after removal of vestibular schwannoma via the retrosigmoid approach: A long-term follow-up-study. Otolaryngol Head Neck Surg 2003 Mar;128(3):387-95

• Shin YJ et al. Effectiveness of conservative management of acoustic neuromas. AM J. Otol 21:857-862, 2000.

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T2

T1 post-Gad

T1 pre-Gad

Hydrocephalic

Compressive

Cisternal

Intracanalicular

Phases of Tumor Growth

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