Facial Innervation Flashcards
1
Q
branchial arches
A
- Embryonic structures or pouches
- These structures are innervated first – you don’t grow a limb and innervate after the fact
2
Q
first branchial arch
A
- 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
3
Q
second branchial arch
A
- Cranial Nerve VII
- To Zanzabar By Motor Car – 5 branches of cranial nerve
4
Q
Facial pain
A
- 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!!
5
Q
trigeminal neuralgia
A
- “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
6
Q
treatment of trigeminal neuralgia
A
- 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)
7
Q
Vascular hypothesis
A
-Compression of CNV at entrance to brainstem, most commonly Superior Cerebellar Artery
8
Q
Facial weakness
A
- 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
9
Q
Bell’s Palsy findings
A
- 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
10
Q
Examination of Bells palsy
A
- Cranial Nerve testing
- Peripheral neruological examination
- Must r/o CVA/TIA, Lyme, herpes Zoster
- Can they close their eyes???
11
Q
etiology of facial palsy (Bell’s)
A
- Idiopathic facial neuropathy attributed to inflammatory reaction of facial nerve
- More common in pregnancy, diabetes
12
Q
Can they wrinkle their forehead
A
- Forehead muscles innervated bilaterally, preserved in Bell Palsy
- The trauma is outside of the CNS, then they can wrinkle forehead
13
Q
Treatment of Bell’s palsy
A
- Steroids may be effective
- Most patients will clear spontaneously with no lingering effects
- Acyclovir not warranted for Bell Palsy
- Tape eyelid to protect cornea
14
Q
resolution of bell’s palsy
A
- 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
15
Q
Classification of peripheral neuropathies
A
- Axonal
- Paranodal/segmental demyelination
- Mononeuropathies by compression
- Polyneuropathies – (hereditary, metaboic, toxic)
16
Q
Mononeuropathies
A
- 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
17
Q
Polyneuropathies
A
- 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
18
Q
Peripheral neurological examination
A
- 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)?
19
Q
Things to look for (motor)
A
- 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)
20
Q
Things to look for (sensory)
A
- 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
21
Q
Inherited innervation disorders
A
- Friedreich’s Ataxia
- Porphyria
22
Q
Freidreich’s ataxia
A
- 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
23
Q
Pathology of Freidrich’s ataxia
A
- 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
24
Q
Systemic metabolic disease of facial innervation
A
- 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)
25
Diabetic neuropathy
- 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
26
Pathophysiology and managment of diabetic neuropathy
- 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)
27
Guillain Barre Syndrome
- 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
28
GBS physical exam
- 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
29
Carpal tunnel
- 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)
30
exam for carpal tunnel
- 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!!
31
treatment of carpal tunnel
- 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
