Clinical Correlations

Question 1

Oculocephalic Maneuver (Dolls eye Maneuver)

Answer 1

• Can be applied to comatose patient. - The examiner turns the head of the PAT in the horizontal (or vertical) plane and notes whether the ocular excursion in the opposite directions occur.

Question 2

Caloric Testing of the Vestibulo-Ocular Reflex

Answer 2

• Outer ear canal is irgiated with cold and examiner observes for conjugate deviation of the eyes. - Cold water in the Left ear, inhibits the left labyrinth. Right labyrinth is neutral - Hot water in the left ear activates the the left labyrinth.

Question 3

Bell’s Palsy (Facial Paralysis)

Answer 3

• Peripheral lesion of the facial nerve, due to swelling and compresion in the distal part of the bony facial canal. - In addition patient present with a flattened nasolabial fold + unable to raise eyebrows and wrinkle the forehead on affected side.

Question 4

Otosklerosis

Answer 4

• Gradual replacement of normal bone of the bony labyrinth and the stapes footplate by lamellar new bone. - Leads to a fusion stapes with the borders of the oval window. - Conductive Hearing loss up to an 40 dB sound pressure level

Question 5

Meniere’s Disease

Answer 5

• Abnormalities of endolymph circulation lead to significant dilation of endolymph compartments & degeneration of hair cells. - Disease affects vestibular & auditory system. - Characterized by vertigo, tinnitus and sensorineural hearing loss

Question 6

Presbyacusis

Answer 6

• Presbyacusis or age related hearing loss, is progressive bilateral and symmetrical sensorineural hearing loss associated with aging.
• Pathology: damaged hair cells, peripheral nerve damage, damage to central auditory pathway

Question 7

Internuclear Ophtalmoplegia

Answer 7

• Lesion of the Medial Longitudinal fasciculus (MLF) - Prevention conduction on the eye on the side of the lesion during attempted lateral gaze - Convergence does not involve the MLF and its not afected by the lesion

Question 8

PPRF Lesion

Answer 8

• Paralysus of horizontal eye movements. Conjugate horizontal gaze towards the side of the lesion is interrupted.

Question 9

One-and-half Syndrome

Answer 9

• Lesion of PPRF and MLF on same side of braintem (due to extensive paramedian pontine lesion) - Ipsilateral of Lesion: NO abduction & NO adduction during conjugate horizontal gaze - Contralateral: NO adduction durong conjugate horizontal gaze

Question 10

Antibiotics (Streptomycin) Vestibulo - Ocular reflex

Answer 10

• Antibiotics can be toxic to vestibular hair cells. Antibiotics accumulate in the endolymph and cause damage to the vestibular system.

Question 11

Pathological Vestibular Nysagmus

Answer 11

• Damage to the vestibular systme on one side canc ause a pathilogival form of vestibular nystagmus. - Slow nystagmus is directed towards the inactive, damged labyrinth. - Fact component (reset) is directed towards the active (still functional) labyrinth.

Question 12

Vestibular Schwannoma

Answer 12

Benign Tmor originating from Schwann cells of the vestibular division of CN VIII. THe tumor compresses the vestibulo-cochlear nerve within the internal auditory meatus. —> Sensorineural hearing loss

Question 13

Wallenberg (Lateral Medullary) Syndrome

Answer 13

• Cause: Occlusion of the PICA - Manifestations are: . Ipsilateral facial anesthesia/thermanesthesia: Spinal nucleus of trigeminal nerve . Contralateral extrafacial anesthesia/thermanesthesia: Anterolateral system . Ipsilateral ataxias, uncooordination: Inferior cerebellar peduncle . Vertigo and nystagmus: Vestibular nuclei . Dysarthria and dysphagia: Vestibular nuclei . Horner Syndrome: Disruption of hypothalamo-spinal fibers

Question 14

Hypogeusia

Answer 14

• Decreased Taste function - Can be due to pathology of oral cavity, secondary to salivary gland dysfunction, leading to taste bud destruction

Question 15

Ageusia

Answer 15

• Loss of taste function - Lesion of chorda tympani of CN VII (Bell’s palsy), which occurs unilaterraly, and causes ipsilateral loss of taste from Ant 2/3 - Another cause: Wallenber’s syndrome due to infarction of PICA

Question 16

Hyposmia

Answer 16

• Decreased smelle function.

Question 17

Anosmia

Answer 17

• Total loss of smell function. - Compression of olfactory by tumors, especially meningeomas.

Question 18

Retinitis Pigmentosa

Answer 18

• Rods degenerate - Earliest Symptoms: night blindness followed by loss pf peripheral vision, leading to tunnel vision. - Photoreceptor degeneration is associated with reduced phagocytosis by RPE cells during the process of disk shedding.

Question 19

Frequency Code

Answer 19

• Frequency of action potentials in afferent fibers increases with sound intensity.
• This refers to the frequency of action potentials, and not to be confused with the frequency of sound.

Question 20

Volley Code

Answer 20

• A mechanism to encode sound intensity, based on the # of afferent fibers activated.
• Each individual inner hair cell synapses on 20 auditory nerve fibers with different sensitivity thresholds.
• Low intensity sound only activates low threshold fibers. Higher sound intensity recruit more afferent fibers with higher thresholds.

Question 21

Motion Sickness (Kinetosis)

Answer 21

• Individuals experience a discrepancy between vestibular and visual inputs.

Symptoms: dizziness, vomiting and seating.

Question 22

Alcohol Intoxication

Answer 22

• Can produce vestibular symptoms.
• It is caused by intereaction og blood alcohol with endolymph, which causes convection endolymph flows within the semicircular canals.

Question 23

Tabes Dorsalis

Answer 23

• Due to syphilitic infection.
• Destruction of dorsal root ganglion with large diameter myelinated axons causes severe deficit in touch and proprioception.
• Nociception and temperature sense remain almost unaffected.

Question 24

Diabetic Retinopathy

Answer 24

• Initial phase, smaller scotomas are not recognized by the patient. As soon as the macula is involved, the visual loss increased dramatically.
• The retina defects are caused by blood supply dysfunction including reduction of permeability of basal memebranes of capillary endothelial cells and bvessels

Question 25

Aminoglycoside antibiotics

Answer 25

- Neomycin and streptomycin inhibit exocytosis of ACh at motor nerve terminals by blocking presynaptic Ca+ channels. - At high concentration both antibiotics can block postsynaptic nAChRs - Can be reversed by raising extrac calcium.

Question 26

4-Aminopyridine

Answer 26

- K+ channel blocking drug prolongs the duration of the impiulse --\> increases Ca2+ entry. - This raises the probability of ACh release and hence quantum content.

Question 27

Lidocaine & Procain

Answer 27

Block voltage-gated Na+ channels