Pathophysiology of Sensory Systems ( Eye & Ear )

Question 1

Explain the Hearing pathways ( Sensory )

Answer 1

1- CN8 comes in from the basilar membrane in cochlea
2- travels to cochlear nuclei I the Brian stem
3- travels to inferior colliculus in midbrain
4- travels to medial geniculate nucleus in the thalamus
5- Go into sylvan fissure where auditory cortex is in the temporal lobe ( tonotopic map )

Most fibres travel contra laterally , some do ipsilaterally

Question 2

How do fibres travel in the Hearing Pathway

Answer 2

Most fibres travel contra laterally , some do ipsilaterally

Question 3

What are the association areas for Hearing

Answer 3

Wernickes area : understanding and processing of language

Close to auditory cortex

Question 4

What is Conductive Deafness

Answer 4

Difficulty in getting sound waves and relaying them from the outer ear into the cochlea.

Question 5

What is Sensorineural deafness

Answer 5

Problem converting mechanical vibration into nerve energy. Problem in the cochlea it self or anywhere from the cochlear nerve to the auditory cortex

Question 6

Common causes of Conductive Deafness

Answer 6

1- Auditory canal : wax
2- Middle ear :
-ruptured tympanic membrane (pressure difference)
- otitis media: infection causing fluid in middle ear
- otosclerosis ; harding of the ossicles

Question 7

What are the Causes of Sesnsorineural deafness

Answer 7

1- Cochlea :

• result from aging
• acoustic trauma ( sound pollution , damaging high frequency ) - bc loud noises
• Meniere’s disease : inflammation of membranes of the Cochlea

2- Cochlear nerve : Acoustic neuroma ( growth on CN8)

3- Central auditory pathways ( rare ) :

Question 8

What is Presbycusis

Answer 8

Age related hearing loss : gradual loss of hearing

Question 9

What are the signs of Meniere’s disease

Answer 9

1- Vertigo
2- Tinitus
3- potential hearing loss

All due to increase of fluid

Question 10

How to distinguish between sensorineural or conductive deafness

Answer 10

Rinnes test : compares bone and air conduction

• Positive = Air>Bone = normal or sensorineural deafness
• Negative = Bone>Air = Conductive Deafness

Webers test : midline source of bone conduction, running fork at forehead

• should hear it the same in both ears
• might be better in the ear with conductive deafness

Audiometry : playing tones at different frequencies and seeing degree of hearing loss - Can localize where the damage is depending on frequencies

• Can’t hear Low : meniere’s
• Can’t hear High : acoustic trauma

Question 11

Conductive Deafness would have a positive or Negative Rinnes test and why

Answer 11

Negative
Should be able to hear better via the air conduction than from bone conduction. If that is not the cause then air conduction is being blocked by something

Question 12

What is the purpose of snellen’s chart , what is normal ?

Answer 12

Tests refracting power and accuracy of the lens.

Normal vision : 6/6 meters away can read the 6th line

Question 13

What is the purpose of visual field test

Answer 13

To see if there are areas of the retina that are being damaged.

Question 14

What are the types of refractive defects

Answer 14

1- Presbyopia : Loss of elasticity , receding near point , due to Age
2- Myopia : focussing power too great for eyeball length, needs divergent ( concave ) lenses
3- Hypermetropia: focusing power inadequate for eye length , convergent length

Question 15

Explain Light Pupillary reflexes

Answer 15

1- Light sources travels down optic nerve into LGB
2- into pretetal nuclei to Edginer Westphal Nuclei in CN3
3- Into Ciliary ganglion and then to Sphincter pupillae

Question 16

Explain the pathway for Sympathetic pupil dilatation

Answer 16

Exit the T1 , synapses in superior cervical ganglion and then via long ciliary nerve it travels up internal carotid, then affects dilator pupil muscles

Question 17

Explain the pathway for parasympathetic pupil constriction

Answer 17

1- Signal travels along preganglionic CN3 , then ciliary ganglion to ciliary nerves which stimulates sphincter pupillae

Question 18

Explain Accommodation Pupillary reflexes

Answer 18

1- Light sources travel down Extraocular spindles+ Optic nerve
2- LGB to convergence centre
3- To Edginer Westphal Nucleus ( CN3 ) to Ciliary Ganglion
4- To sphincter pupillae = constricting

Question 19

What is Horner’s syndrome

Answer 19

Sympathetic Lesion

Result : ipsilateral defects , pupillary constriction , ptosis , enopthalmous , sweating loss

Question 20

A dilatation of only 1 pupil to light might mean what

Answer 20

Compression of CN3 resulting in Parasympathetic loss

Question 21

Bilateral pupillary dilatation to light might mean what

Answer 21

Deep coma / Brian death

Question 22

Bilateral pupillary constriction to light might mean what

Answer 22

Pontine lesions or the use of opiates

Question 23

What is Argyll Robertson Pupil ( what causes it )

Answer 23

No light adaptation due to Dorsal Edignger Westphal Nucleus

But Pupil is still constrictiing due to focusing ( accommodation reflex )

Question 24

What could cause Argyll Robertson Pupil

Answer 24

End stage Neurosyphilis

Question 25

What are the Somatosensory Modalities

Answer 25

Touch , vibration , proprioception , pain , temperature

Question 26

Symptoms and Signs of Defects to Sensory Pathways

Answer 26

1- loss of Sensation : numbness to touch and clumsiness/ stamping gait
2- Abnormal sensations : tingling, pins and needles, pain

Question 27

If there is problem with C6 dermatome where will the sensations be

Answer 27

Down the Arm

Question 28

Vibration , position and fine touch travel which way in the spinal cord

Answer 28

Ipsilaterally in the Dorsal Column and then cross over int he Medulla

Question 29

Pain, crude touch and Temperature travel which way in the spinal cord

Answer 29

Contralaterally as the cross over in the spinal cord and then travel up

Question 30

Peripheral nerve damage signs

Answer 30

Sense damage where nerve distribution is
1- loss of all sensation
2- Loss of motor activity , lower motor neurone weakened in muscles innervated by that nerve

Question 31

Nerve root damage signs

Answer 31

1- loss of all sensation in affected dermatome

2- lower motor neutron weakness if anterior nerve root is affected

Question 32

Posterior column damage Signs

Answer 32

Ipsilateral sensory defects below level of defect involving position, vibration and light

Question 33

Spinothalamic tract damage signs

Answer 33

Contralateral sensory defects below level of defect for pain , temperature and crude touch

Question 34

Bilateral spinal cord damage signs

Answer 34

Loss of all sensation and bilateral UMN weakness below level of lesion

Question 35

Brown-Sequard Syndrome Signs and Symptoms

Answer 35

1- Ipsilateral loss of proprioception, vibration and light touch below the lesion
2- contralateral loss of pain , temperature and crude touch below lesion
3- ipsilateral UMN weakness below lesion but LMN signs at level of lesion

Question 36

Brain stem lesions Signs ex: midbrianstem

Answer 36

Contralateral sensory defects below site of damage.

Ipsilateral loss of facial sensation ( trigeminal sensory nucleus )

Question 37

Lesion above the brainstem signs ex: thalamus

Answer 37

Contralateral sensory loss in face and body

Question 38

Signs of Polyneuropathy / peripheral neuropathy

Answer 38

1- Glove and stocking : symmetrical peripheral loss of sensation in hands and bottom legs , that ascends
2- affects excitability and conduction in nerves in the region
3- motor and autonomic defects