Download Case 4 - A deaf man with poor balance - Ipswich-Year2-Med

Case 4 - A deaf man with
poor balance
Skye and Jackie
TRIGGER 1
A 28 year old man reports increasing tinnitus in
his right ear with a tendency to fall to the
right.
He has no significant previous medical history.
On examination he has right sided ataxia, a
gaze paresis to the left and sensorineural
deafness on that side.
Q1 Where is the lesion?
Q1 Where is the Lesion?

“The lesion is clearly involving the right pons,
right side of the brainstem or cerebellum and
presumably the 8th cranial nerve on the right
given the deafness. It is therefore likely that the
lesion is in the cerebellar pontine angle on the
right”

Q2 What is the lesion likely to be?
Q2 What is the lesion likely to be?

PDX: Acoutic Neuroma

DDX: meningioma, developmental cysts, malignant
middle ear infection, malignant otitis externa

“Given the position the most likely cause of this is an acoustic neuroma
which is a Schwannoma of the vestibular part of the 8th cranial nerve. There
are a number of other lesions in this anatomical location that could give this
clinical picture including meningiomas as well as different types of
developmental cysts”.
“Some patients develop malignant middle ear infections where the infection
is such that it erodes the bone and destroys the local structures. In younger
people this can take the form of cholesteatoma, in older patients especially
diabetics it can often start in the external ear and they develop a malignant
otitis externa”.
Neuroscience at a Glance

Clinical Reasoning: Up-to-date



Cochlear nerve —Symptomatic cochlear nerve involvement occurred in 95 percent
of patients. The two major symptoms were hearing loss and tinnitus. Hearing loss
was present in 95 percent but only two-thirds of these patients were aware of this
limitation.
Vestibular nerve — Involvement of the vestibular nerve occurred in 61 percent of
patients . Affected patients frequently acknowledged having unsteadiness while
walking, which was typically mild to moderate in nature and frequently fluctuated in
severity. True spinning vertigo was uncommon. The most nondescript vertiginous
sensations, such as brief tilting or veering, can suggest the presence of a vestibular
schwannoma.
Trigeminal nerve — Trigeminal nerve disturbances occurred in 17 percent of
patients . The most common symptoms were facial numbness (paresthesia),
hypesthesia, and pain. The average duration of symptoms was 1.3 years; the
symptoms usually occurred after hearing loss had been present for more than two
years and vestibular symptoms for more than one year. Facial nerve — The facial
nerve was involved in 6 percent of patients . The primary symptoms were facial
paresis
BUT….
Q3 Why does he have a gaze paresis?
Q3 Why does he have a gaze paresis?

Gaze Paresis: a disturbance of eye conjugate movement in which gaze
tends to be tonically deviated in the direction of normal gaze. For example,
in left frontal lobe damage the patient cannot voluntarily look to the right and
the eyes spontaneously deviate to the left. The patient may be able to return
the gaze voluntarily to the midline but cannot move the eyes past the
midline into the paretic field of gaze.

“This reflects compression of the left pontine area in particular the
pontine paramedian reticular formation which is responsible for
horizontal gaze”

Lesions of the sixth nerve nucleus cause paralysis of gaze to the side of the
lesion. If fibers from the opposite 6th nerve nucleus are involved as they
cross to the MLF, there is also weakness of the ipsilateral medial rectus
muscle.
NOTE: patients with hemisphere lesions look toward their lesion, while
patients with pontine gaze palsies look away from their lesions. Note that
patients with gaze palsy still have conjugate eye movements and therefore
do not complain of diplopia.

Q4 Would you initially do a lumbar
puncture in this man to help in the
diagnosis?

No indication for LP in this case. I.e. no infection, no
suspected SAH, no instillation of chemotherapy.
Q5 What (other) tests would be helpful in the
diagnosis of this man?
Q5 What (other) tests would be
helpful in the diagnosis of this man?
Examination

Physical examination. Identify other sources of symptoms and any concurrent disorders

Otoscopic examination. Rule out other causes of hearing loss, assess general ear condition. Do not
discontinue further investigation when eardrum is normal but there is unilateral hearing loss or tinnitus

Complete neurologic examination. Pay special attention to the cranial nerves
Summary of tests

Audiometry to determine hearing loss and establish a baseline prior to further observation or
therapeutic intervention: (1) pure tone, (2) speech discrimination (most often affected in patients with
acoustic neuroma even when pure tone audiometry is normal), and (3) speech threshold

MRI with gadolinium enhancement is the gold standard for diagnosis and should be performed early
in the investigative process whenever possible. Can be done before referral to ENT specialist if MRI
facilities are available. Expedites definitive diagnosis. (Fast spin echo MRI has also been investigated
for the detection of acoustic neuroma, although it does not reliably identify small tumors)

CT scan with contrast may be performed if necessary in cases where an MRI is not available or
cannot be performed but it is limited to identifying tumors 1cm or greater in diameter

Auditory brainstem response test may be done in some cases to determine interruption of electrical
impulses through the auditory nerve to the brainstem. A negative result does not rule out acoustic
neuroma. (Provides information about the transmission velocity of electrical impulses along the
acoustic nerve from the inner ear to the brainstem pathways)
Q6 Should his family be told they are at risk of developing similar problems?
Q6 Should his family be told they are
at risk of developing similar problems?

No, as acoustic neuromas are rarely inherited. If they are
bilateral in nature, however, this implies that they might have a
condition called neurofibromatosis type II in which case genetic
testing and counselling would be advised.

Neurofibromatosis type 2 (NF2) is a dominantly inherited
syndrome that predisposes individuals to multiple tumors of the
nervous system. The most common of these are bilateral
vestibular schwannomas; intracranial and spinal meningiomas
and spine tumors are also a prominent component of this
condition. Mutations in the NF2 gene, which produces merlin, a
tumor suppressor, are responsible for this syndrome