Anatomy
In what layer of the retina are the photoreceptors located?
Photoreceptors are the deepest cells of the retina meaning light travels through the retinal layers to reach them
What are some of the functions of the brainstem?
What is otitis externa and some of its common clinical symptoms?
Inflammation of the external auditory canal, which is most often the result of a local bacterial infection.
Severe ear pain, particularly at night
Otorrhea
Intense itching in the EAC
Hearing loss
Jaw pain
What are the two general types of syncope?
Cardiac vs noncardiac syncope
What muscle is associated with the superior tarsal plate? What is its action and innervation?
Levator palpebrae superiors muscle, innervated by the oculomotor nerve (CN III) functions to elevate the upper eyelid (opens the eye)
Which cranial nerves have nuclei in the midbrain of the brainstem?
3 - oculomotor
4 - trochlea
5 - trigeminal
What is Horner's Syndrome and what are its clinical features?
Horner syndrome (HS) is a neurological disorder characterized by a symptom triad of miosis (an abnormally small pupil due to loss of tone in pupillary dilator muscle), partial ptosis (drooping of the upper eyelid due to loss of tone in superior tarsal and orbitalis muscles), and facial anhidrosis (absence of sweating).
This condition results from lesions that interrupt the ipsilateral sympathetic nervous supply to the head, eye, and neck (nb: depends on area of lesion refer to extra notes). Most cases of HS are idiopathic, but conditions such as brainstem stroke, carotid dissection, and neoplasm are occasionally identified as the cause of HS.
What would a palsy in the abducens nerve (CNVI) result in?
Horizontal diplopia
What is the function of suspensory/zonular ligaments?
Connects ciliary muscle to lens, muscular tension on these ligaments determines the thickness of lens
What is the afferent and efferent cranial nerve limbs for the carotid sinus reflex?
Afferent → glossopharyngeal nerve (IX)
Efferent → vagal nerve (X)
Why would an optic nerve deficit affect pupil constriction?
Optic nerve (CNII) is the afferent arm of the pupillary light reflex, therefore if it is damaged then sensory information for the pupillary light reflex cannot trigger pupillary constriction or dilation via oculomotor nerve (CNIII)
Why does demyelination selectively affect CNII more than other CNs?
CN1+2 are part of the CNS unlike other cranial nerves which are part of the PNS, this means that the neurons are myelinated by different cell populations i.e. oligodendrocytes vs Schwann cells respectively, and these cell populations are differentially susceptible to demyelination (oligodendrocytes more susceptible)
What are the divisions of the retina based on vascular supply?
Retina has dual blood supply ∴ divided into outer and inner retina
Outer retina served by the choroid: Retinal Pigmented Epithelium (RPE) to outer plexiform layer where photoreceptors and bipolar cells synapse (indicates high metabolic rate)
Inner retina served by the central retinal vessels
Describe the general pathway of aqueous humour drainage
Ciliary body produces aqueous humour → posterior chamber → through the pupil (between iris and lens) → anterior chamber → canal of Schlemm → episcleral vessels
How can you differentiate between vestibular neuritis and labyrinthitis?
Hearing loss present in labyrinthitis
What is meniere disease and its triad of symptoms?
Meniere disease (endolymph hydrops) is a disorder of the inner ear caused by impaired endolymph resorption (The exact etiology of endolymph malabsorption is unknown).
Meniere triad: Peripheral vertigo,Tinnitus, Asymmetric fluctuating sensorineural hearing loss (SNHL)
What is Uthoff's phenomenon?
A reversible exacerbation of neurological symptoms following an increase in body temperature, e.g., physical exertion, a warm bath, or fever
As impulse conduction is dependent on temperature an increase in body temperature presumably worsens impulse conduction in demyelinated nerves.
What is the reticular system, its two main divisions and their respective functions?
Combination of multiple neurons and tracts within the brainstem controlling multiple functions
Above mid-pons: sends ascending pathways to thalamus and cortex to control arousal (and therefore level of consciousness)
Below mid-pons: mediates vital reflexes related to: breathing (coughing, sighing and hiccupping), feeding (sucking, chewing, salivating, gagging, vomiting), homeostasis, control of BP and pulse, alimentation and elimination, control of posture and eye movements
What are some red flags for tonsillopharyngitis?
Trismus
Drooling
Asymmetric tonsils
Displaced uvula
Unilateral facial swelling
Muffled or “hot potato” voice
Clinical features of sepsis
Immunosuppression
In CNVII palsy, why is it important to identify whether the forehead is spared or not?
Can distinguish between an upper or lower motor neuron lesion
As the forehead region is controlled by both hemispheres (contralateral and ipsilateral primary motor cortexs) an upper motor neuron lesion on one side would be forehead sparing due to the compensation of the other side. The lower face is only controlled by the contralateral primary motor cortex.
A lesion of the lower motor neurons would disrupt all motor neurons to the face and therefore the forehead would be affected e.g. in Bell's palsy