Neurootology

Question 1

A 50-year-old male banker present with several month history of a “ hissing steam” sound in the left ear associated with occasional muffled hearing, he has had five episodes of profound vertigo that were sudden in onset and have twice forced him to the ground for a 5 to 15 minutes. He experienced nause and vomitting with most episodes and had to rest for several hours after each ‘attack’ magnetic resonanceimaging of the brain is normal. An audiogram identifies low frequency hearing lost with preserved speech discrimination. What is the most likely diagnosis :
A. Vestibular neuritis
B. Acoustic neuroma
C. Meniere’s disease
D. Benign positional vertigo
E. Vertebro-basilar insuffciency

Answer 1

C. Meniere’s disease

Labyrinthine desease is the most common cause of true vertigo. Meniere’s disease, which is though to be caused by a derangement of endolymphatic fluid regulation. Is the classic variety of labyrinthine disfunction the clinical triad to meniere’s deseaseincludes intermitten severe episodes of disabling vertigo. Tinnitus (often described as resembling the sound of escaping steam), and fluctuating flow frequency hearing loss. Attacks may last several minutes and often several require several hours of full recovery. Nausea, vomitting, and diaphoresis often acommpany the vertigo. A small portion of patients with meniere’s desease experience sudden, violent falling attacks. Clinical onset is commonly in middle age, and the disorder affect up to 1 per 100.000 population. The fluctuating hearing loss mentioned is common and progress to deafness in the

Question 2

A-61-years old airline mechanic presents with gradually worsening he hearing in his right ear over the last 18 months. He has been uneble to use the telephone with that ear for 6 months. His audiogram (same result for bone and air conduction) is shown in figure 1. Speech audiometry reveals discrimination score of 88% in the left ear that 65 dB and 20% in the right ear at 100 dB. His hearing function is the best describes as :
A. Autosomal recessive deafness
B. Retrocochlear sensoneural hearing loss
C. Occupational high frequency hearing loss
D. Normal

Answer 2

B. Retrocochlear sensoneural hearing loss

The patients described in this question suffers from two problems : 1) bilateral, high frequency, hearing loss and 2) profound right retrocochlear sensoneural hearing loss. His threshold for tones conducted by both bone and air is diminished, consistent with a sensorineural cause of his bilateral high frequency hearing loss (due to his work around loud jet engines). Aging and prolonged exposure to load noise are the most common causes of high frequency sensorineural hearing loss. These causes typically result in symmetric loss of hearing with a characteristic loss in higher (paticulary 400 Hz) frequencies. Because low to mid frequencies are often intact in these persons, speech recognition may be preserved.
Although prolonged exposure to noise might explain the audiological testing results in the patients left ear, the profound loss of hearing on the right raises suspicion of an addtional cause of unilateral hearing loss.

Question 3

In the case of an intracanalicular vestibular scwannoma, what distinguishes the middle cranial fossa approach from the retrosigmoid approach?
A. Decreased risk of injuring the greater superficial petrosal nerve.
B. Early of the identification of the facial nerve
C. Improved preservation of vestibular nerve function.
D. Decreased risk of CSF leak

Answer 3

B. Early of the identification of the facial nerve

Small intracanicular vestibular schwannomas in patients with preserved hearing can be approached via suboccipital or middle fossa approach, the latter allows for early identification of CN VII because of the nerves supero-anterior lacotion in the distal internal auditory canal. Importanly, however, early identification does not necessarily make preservation of the nerve easier, especially if the tumor arises from the inferior vestibular nerve. The greater superficial petrosal nerve (GSPN) may be stretched during elevation of the temporal lobe during the middle fossa approach and thus damaged. Preservation of vestibular nerve is not a distinguishing feature of the middle fossa over the retro sigmoid approach. The CSF leak rate is similiar between the two.