Sachen: Introduction to the Peripheral Nervous System Flashcards
Epineurium
-covers whole nerve
Perineurium
-fascicles (containing fibers)
endoneurium
-invdividual fibers
myelinated nerves
- fast conducting
- saltatory conduction
unmyelinated neres
-slow conducting
smaller the diameter, the ….. the velocity
-the slower
what kind of fibers conduct pain,
small unmyelinated fibers
-the larger slower conducting ones are for motor and s proprioception
points of injury of the nerve
- cell bodye
- nerve root
- peripheral nerve: axon, myelin sheath, CT, blood supply (vasa nervorum)
- Wallerian degeneration
what is the radicular part of the nerve?
-the part that is exiting the spinal cord
What is radiculopaty?
-neve root dysfunction may be caused by structural or nonstructural conditions
Most common levels involved for radiculopathy?
- cervical (C6, C7)
- lumbar (L5-S1)
if a nerve is compressed between C5 and C6, what is the nerve root compression called?
-C6 compression
sclerotome, what does it innervate?
-the perosteum of the bone
C5 radiculopathy
- scapula shoulder
- lateral arm
- shoulder abd weaknes
- DTR loss in biceps
C6 radiculopathy
- scapula shoulder ish
- 1 and 2 digit, lateral arm
- shoulde abd and elbow flex weakness
- DTR lossin biceps
C7 radiculopathy
- scapula, shoulder/arm, elbow/forearm
- 3rd digit
- elbow ext, wrist ext
- triceps DTR loss
C8
scapula, shoulder/arm, medial forearm
- 4 and 5 digit
- finger abd and flex weakness
- loss of DTr in finger flexors
L4 radiuclopathy
- antlat thigh, knee, medial calf pain
- medial calf sensory loss
- hip flexion, knee ext weakness
- DTR loss in patella
L5 radiculopathy
- dorsal thigh lat calf pain
- lat calf dorsum foot sensory
- hamstrings, foot dorsiflexion, inversion, everion weakness
- no DTR loss
S1 radiculopathy
- post thigh, post calf pain
- post lat claf and lat foot sensory
- weaknessin hamstrings and foot plantarflex
- DTR loss in achilles
Do roots split fingers?
-no they don’t
is T1 dermatome on the chest?
- no, it’s on the posteriormedial arm!
- watch out for this
Mononeruopathy
- single nerve is affected
- specific pattern of sensory loss
- weakness only in specific muscles
Polyneuropathy
- diffuse, symmetrical disease… motor sensory, or both
- stocking/glove sensory loss
- distal weakness, possibly atrophy
- hypo or arreflexia
Mononeruopathy multiplex
- focal involvement of two or more nerves
- may occur in some systemic disorders (DM, vasculitis)
Negative sx of peripheral nerve disease
-loss of sensation
positive sx of peripheral nerve disease
- paresthesias.. secondary to large myelinated fiber disease “pins and needles”
- pain, secondary to small unmyelinated fiber disease…. burning and dysesthesia
Motor sx for peripheral nerve disease
- distal weakness
- cramps
- muscle fasciculations
- atrophy
- decreased eep tendon reflexes
- reduced tone
what is the etiology of the sensory problems in peripheral nerve disease
-large myelinated sensorty fibers… impariment of light tocuh, 2 pt, bibration, joint position sense
if small unmyelinated sensory fibers are impaired, what will there be?
- temp perception problems
- pain perception (pin prick)
what muscles do we have to look at if there is a radiculopathy?
- paraspinal muscles
- they have nothing to do with a plexopathy though
most common site of nerve compression
- median nerve
- carpal tunnel
Median nerve distribution
-medial palmar surface of the lower forearm and palm, thenar eminence, thumb, and adjacent two and a half fingers
clinical features of pronator syndrome
- insidious onstet of diffuse ache about the prox forearm
- pain exacerbatino with forced foreamr pronation
- easyu fatigue of the forearm muscles
- diffuse numbnees of the hjand mostly involving the 2 and 3 fingers
- **absence of nocturnal awakening becuase of pain or numbness
anterior interosseous syndrome
- nerve conductino studies: routind meidna nand ulnar studies are normal
- needle EMG: abnormaltieis in FPLm, DFDP, PQ
- other median, medial cord, C8, muscles normal
Ulnar mononeruopathy
- axilla
- elbow
- cubital tunnel
- wrist: guyons canal
Froments sign, what is that for?
- Ulnar neuropathy
- if they can’t hold a piece of paper with their thumb
Radial mononeruopathy
- axilla: crutch palsy
- humerus/ spiral groove: saturday night palsy… most common
- supinator (posterior interosseus branch)
- wrist (superficial radial sensory branch)
Radial nerve
- as it winds around the humerus, it is culnerable to compression
- radial nerve damage leads to the readily recognizable wrist drop that results from paresis of teh extensor muscle of the wirst, finger, and thumb
clinical features of radial mononeruopathy
- compressive lesion with good prognosis
- weakness of wriste and finger extension
- elbow extension spared
- brachioradialis spared sometimes
EDX features of spiral groove radial mononeuropathy
- radial motor and sensory studies often normal
- emg findings in extensors of wrist and digits and perhaps brachioradialis
What is the dermatome for the L5 radiculopathy?
- the same as the peroneal nerve
- lateral part of the calf
peroneal vs L5 radiuclopathy… how do we tell between them?
- test foot inversion
- if weak, L5 (this one innevates inversion muscles)
- if it’s fine, then it’s peroneal (doesn’t innervate inversion muscles)
peripheral neuropathy
- usually symmetric
- may be motor, sensory, autonomic or combo
- usually progressive, butnot always
- aquired or inherited
difference between small and large nerve involvement
- large nerves: position/vibratory sense
- small: pain and temp sense
How does peripheral neuropathy present?
- pain, sensory loss, weakness occurs symmetrically and most severly in the distal portions of the limbs
- the legs are usually affected first and more severely than the arms
- this distribution is termed “stocking glove” (hands and feet)
What are the big etiologies of peripheral neuropathy we have to worry about?
- lyme disease
- HIV
- Guillane barre
- Monoclonal gammopathy
what drugs will cause peripheral neuropathy?
-vinca alkaloids, phytoin, isoniazid, amiodirone, cis platinum
CMT1
-demyelinating
CMT2
- axonal/neuronal
- later life presentation
- less common than 1
How will the foot look like in CMT?
- high arch, curled toe
- remember that there is variable penetrance with this disease,….. so not all of their families will have this
Porphyria
- defect in heme biosynthesis
- this always presents as belly pain, so get’s mismanaged by GI things
- hereditary neuropathy with liability to pressure palsies
Fabry’s disease
-alpha galactosidase deficiency
Metachromatic leukodystrophy
- arylsulfatase a deficiency
- affect both central and peripheral nerve
Tangier disease
-deficiency in HDL
PHytanic acid storage diseas
they will have orange tonsils… fun
Acquired demyelinating polyneuropathies
- Guillane barre syndrome
- chronic inflammatory demyelinating polyneuropathy (CIDP)
- multifocal motor neuropathy (MMN)
- multifocal acquired demyelinating sensory and motor neuropathy
Guillan barre syndrome
- acute/subacute ascending motor paralysis
- often an antecedent illness, surgery, immunization: EBV, mycoplasma pneumonia, campylobacter jejuni enteritis
- HIV
- Hodgkin’s disease
Key lab findings with Guillaine barre
- CSF: albumino-cytologic dissociation (high ptn/normal cell count/normal glc)
- NCVs: slow conduction vleocity, focal conduction block, prolonged F waves
tx of guillaine barre?
- supportive care
- direct tx with plasma exchange or IVIg
Prognosis of Guillain Barre syndrome
- 25 % require mechanical ventilator support
- most recover in weeks to months
- death in about 2-10%
- persistent disability in about 20%
- poor prognosis associated with NCV/EMG findings of low amplitude motor nerve responses and/or denervation as this implies axonal involvement
Miller-fisher syndrome
- variant of guillan barre
- opthalmoplegia, ataxia, arreflexia
- facial weakness, dysarthria, dysphagia also possible
- GA1b and GT1a antibodies
-Chronic inflammatory demyelinating plyneuropathy (CIDP)
- similar to GBS but slower to evole and more persistent
- may occur de novo or as sequellae of GBS
- progressive or repasing course
- 15% have a monoclonal antibody
- tx: IVIg, steroids, plasma exchange, immunosuppressie agents
Multifocal motor neuropathy clinical findings
- adults, male moreso…. initially in distribution of a single nerve
- slowly progressive distal weakness of hands>feet
- no sensory signs/symptoms, no UMN signs
Lab findings for Multifocal motor neuropathy
- elevated serum GM1 antibody
- EMG shows conduction block or other demyelinating features
- CSF usually normal
Tx for multifocal motor neuropathy
- IVIg is tx of choice
- other immunosuprressants as secondary option
Diabetes mellitus
- most common identifiable cause of neuropathy in the US
- many different forms of nerve things
HIV neuropathies
- some pts get this
- distal smmetrical polyneuropathy
- acute inflammatory demyelinating polyneuropathy
- CIDP
What is Charcot Marie tooth disease known as in this lecture?
-Hereditary motor and sensory neuropathies
What do we look for if there is hx of exposure/rash?
-lyme antiboyd titer
systemic vasculitis, what lab do we want to run?
-aANCA
Anti MAG, what does that test for?
-MGUS associated neuropathy
Anti GM1, what does that test for?
-Mutlifocal motor neuropathy
What antibody do we look for if there is miller fisher syndrome?
-Anti GQ1b
What does Hu antibody mean?
-carcinomatous sensory neuropathy
Urine tests for specific conditions
- heavy metals…. wuith hx of exposure and clinical profiles
- immunoelectrophoresis…. rarely positive when serum EP is normal
