Facial Innervation

Question 1

branchial arches

Answer 1

• Embryonic structures or pouches

- These structures are innervated first – you don’t grow a limb and innervate after the fact

Question 2

first branchial arch

Answer 2

• Cranial Nerve V
• The trigeminal nerve innervates the products of the first arch because it innervates the arch!!
• The nerve gets pulled and stretched and innervates these structures

Question 3

second branchial arch

Answer 3

• Cranial Nerve VII

- To Zanzabar By Motor Car – 5 branches of cranial nerve

Question 4

Facial pain

Answer 4

• MCC = dental, triggers include hot, cold, sweet foods
• Short, electric shock like facial pains (“Lancinating”), in specific nerve distributions = neuralgias
• Pain = CN FIVE!!!!!
• If presentation is facial pain, you are NOT talking about facial nerve!!

Question 5

trigeminal neuralgia

Answer 5

• “tic douloureux”
• Short, excruciating pains in V2 or V3 divisions
• Mid-old age
• Pain at trigger points, without sensory deficit (There is NO lack of sensation)
• Onset in young adult or bilateral – think MS

Question 6

treatment of trigeminal neuralgia

Answer 6

• Neuropathic pain – AVOID narcotics
• AED’s have proven effective: Carbamazapine, phenytoin, gabapentin (Titrate up to therapeutic level – if you don’t, risk seizures)
• Surgical option if medication fails (Usually attempts to relieve decompression by tortuous vasculature in the posterior fossa or along path of CN V)

Question 7

Vascular hypothesis

Answer 7

-Compression of CNV at entrance to brainstem, most commonly Superior Cerebellar Artery

Question 8

Facial weakness

Answer 8

• Look for symmetry
• Define muscle groups involved
• Loss of taste or hyperacusis? (7, 9, and 10) (Hyperacusis = things sound louder (7, chordae tympani))
• Vesicular rash? Shingles? HSV1? (Ramsay Hunt (eruption in pharynx, ear canal distinguish), geniculate ganglion vs CN VII)
• Assess for other neurological signs – isolate facial nerve

Question 9

Bell’s Palsy findings

Answer 9

• Abrupt facial paresis
• Pain around ear may accompany or precede symptoms
• Face feels stiff and pulled to side
• Disturbance of taste is common
• Hyperacusis
• Can happen because of compression, car crash, etc.
• Many times we think its infectious and for that reason, we think treatment with steroids is controversial

Question 10

Examination of Bells palsy

Answer 10

• Cranial Nerve testing
• Peripheral neruological examination
• Must r/o CVA/TIA, Lyme, herpes Zoster
• Can they close their eyes???

Question 11

etiology of facial palsy (Bell’s)

Answer 11

• Idiopathic facial neuropathy attributed to inflammatory reaction of facial nerve
• More common in pregnancy, diabetes

Question 12

Can they wrinkle their forehead

Answer 12

• Forehead muscles innervated bilaterally, preserved in Bell Palsy
• The trauma is outside of the CNS, then they can wrinkle forehead

Question 13

Treatment of Bell’s palsy

Answer 13

• Steroids may be effective
• Most patients will clear spontaneously with no lingering effects
• Acyclovir not warranted for Bell Palsy
• Tape eyelid to protect cornea

Question 14

resolution of bell’s palsy

Answer 14

• 60% recover c/o treatment
• Only 10% with permanent disfigurement or disability
• Assess severity in early disease
• Poor prognosis associated with age, hyperacusis, severe early pain
• Treatment: Steroid controversial

Question 15

Classification of peripheral neuropathies

Answer 15

• Axonal
• Paranodal/segmental demyelination
• Mononeuropathies by compression
• Polyneuropathies – (hereditary, metaboic, toxic)

Question 16

Mononeuropathies

Answer 16

• sensory and motor symptoms in distribution of affected nerve – loss of function in the nerve
• Usually traumatic – related to compression of the nerve
• MC: ulnar, median (carpal tunnel), peroneal (where it passes head of fibula on the outside of the knee
• Predisposition: pregnancy, DM, arthritis, tumors

Question 17

Polyneuropathies

Answer 17

• Toxic, metabolic in nature
• Intermittent symptoms -> normal exam, especially early
• Positive (paresthesias) and negative (numbness) symptoms
• Begin distally, usually (stocking-glove distribution) (Metabolic conditions affect the longest nerves first )
• Sensory before motor (usually, not always)
• Can have a normal exam, particularly early in the disease
• Classic = diabetic neuropathy

Question 18

Peripheral neurological examination

Answer 18

• Is mental status intact? – start at the top and evaluate the entire nervous system so that you don’t miss something
• Are findings symmetric and widespread? (If its multiple nerves, it’s a polyneuropathy, If it’s a polyneuropathy, it’s probably metabolic in nature)
• If findings are abnormal, where is the lesion (know your anatomy)?

Question 19

Things to look for (motor)

Answer 19

• Body position during movement (Paralysis? Reduced arm swing (paralysis)? Compensations?)
• Involuntary movements (Fasciculation, tremor, twitches)
• Muscle bulk and tone (Denervation)
• Muscle strength
• Coordination (Road test)

Question 20

Things to look for (sensory)

Answer 20

• Pain and temperature (spinothalamics)
• Position and vibration (posterior columns) (Fingers and toes first – because they are the furthest and if they aren’t affected, then nothing else probably is either)
• Light touch (both)
• Discriminative sensations (involve cortical input)
• *sensory testing habituates quickly, be specific and efficient
• **compare left v right, distal v proximal
• *** vary pace of examination
• **Sharp v dull with a pin

Question 21

Inherited innervation disorders

Answer 21

• Friedreich’s Ataxia

- Porphyria

Question 22

Freidreich’s ataxia

Answer 22

• Presents in childhood (5-15), early adulthood
• AR disorder, Chr 9 (most prevalent inherited ataxia; 1:50,000, M=F)
• Gait is first disturbance
• Gait ataxic, hands clumsy, other cerebellar signs with leg weakness, extensor plantar response
• Peripheral sensory nerves involved eventually
• Loss of reflexes

Question 23

Pathology of Freidrich’s ataxia

Answer 23

• Extensive corticospinal degeneration
• Loss of cells in dorsal root ganglion
• Degeneration of peripheral sensory fibers
• Loss of posterior columns
• Sensory conduction reduced, motor conduction normal
• If its Babinski, its upper motor neuron

Question 24

Systemic metabolic disease of facial innervation

Answer 24

• Diabetes mellitus
• Peripheral neuropathy is most common complication
• Distal symmetric neuropathy most common type
• Stocking glove pattern – axonal process
• Both motor and sensory nerves effected, longer nerves more (foot, loss of ankle reflexes)

Question 25

Diabetic neuropathy

Answer 25

- Sensory before motor - Dulled perception of vibration, pain and temperature - Denervation of small muscles results in toe clawing - Decreased pain, high pressures leads to ulcers - Also effects autonomic nerves – the vagus can be affected which will affect the GI tract - All diabetic patients get a foot exam at every visit. - Combination of loss of sensation, muscle contractures and joint/connective tissue changes alters biomechanics of foot, promoting ulceration with repetitive stress - Also an isolated form and a painful/burning form

Question 26

Pathophysiology and managment of diabetic neuropathy

Answer 26

- Multiple theories (Excess intracellular glucose disrupts normal axonal physiology, causes breakdown) - Vascular-ischemic – most popular theory – inefficient delivery of O2 to nerve cell (Hyperglycemic damage of capillaries) - Laminin (Lack of normal laminin (in the basement membrane), effects growth) - Autoimmune (Immunogenic disruption of endothelium) - Altered neurotrophic effect (Altered production/transport of Nerve Growth Factor)

Question 27

Guillain Barre Syndrome

Answer 27

- acute idiopathic polyneuropathy - Follows infection (Campylobacter), vaccine, surgery (Antibodies to Cj (campylobacter jejuni) cross react with nerve fibers – causes ascending paralysis, Zika vaccine has been associated) - S/Sx: weakness, begins in legs and ascends - Sensory signs less obvious than motor - May be painful - 40% with respiratory complaints – have to be prepared to intubate

Question 28

GBS physical exam

Answer 28

- LE weakness – symmetric - Minimal objective sensory changes, no sensory level - Absent or hypotonic reflexes, Babinski (-), Hypotonia - LAB: Protein on CSF – may resemble a demyelinating condition like MS - Tx: supportive, prepare for ventilatory support

Question 29

Carpal tunnel

Answer 29

- mononeuropathy - compression of a nerve - Entrapment neuropathy, median nerve trapped by transverse carpal ligament - Occurs in systemic diseases, pregnancy and without associated illness - Findings: Pain, Burning, Tingling, Radiation of pain as high as shoulder (This is because the things they do to compensate can cause them pain)

Question 30

exam for carpal tunnel

Answer 30

- Tinel’s - Phalen’s - Two point discrimination testing - Pain exacerbated by manual flexion - Most bothersome at night - Carpal compression test - Thenar atrophy later finding - Nerve conduction testing – DON’T need to do this!!

Question 31

treatment of carpal tunnel

Answer 31

- Modify activity – a lot of people can’t quit their job – if they can stop the thing that’s irritating - Splint, esp at night, in neutral position - NSAIDs – takes 7-10 days to get anti-inflammatory - Corticosteroid injection possible for refractory cases – works very well, very fast, and doesn’t give incentive