Intro To The PNS Flashcards
What’s the relationship between nerve fiber diameter vs conduction velocity? What’s the fastest type? Slowest?
Bigger the fiber, faster the conduction
Alpha motor neuron
Unmyelinated sympathetic nerves
What is Wallerian Degeneration?
Results when a n fiber is cut or crushed > separation from neuron’s cell body > degeneration distal to the injury
What is radiculopathy? Caused by what? Most commonly where?
Dysfunction of the spinal n roots (PNS) causing somatosensory (pain, radiates), LMN, and autonomic (rare) issues
Intervertebral discs, osteophytes, tumors, DM, infections
Commonly arm and leg (unilateral)
- C5-C7
- L4-S1
What’s a sclerotome?
The innervation level to a bone
What sclerotomes cover the scapula?
C5-C8
What are the dermatomes of the hands?
C6 = 1st and 2nd digits C7 = 3rd digit C8 = 4th and 5th digits
What dermatome controls finger flexion and leads to its weakness?
C8
What’s the sclerotome for L4, L5 and S1?
Sacral bone, pts present w/ deep posterior hip pain
Lumbosacral radiculopathy involving L4 causes:
Pain: antlat thigh, knee, medial calf
Sensory: medial calf
Weakness: hip flexion, knee extension
DTR loss: patella
Lumbosacral radiculopathy involving L5 includes:
Pain: dorsal thigh, lat calf
Sensory: lat calf, dorsal foot
Weakness: hamstrings, foot dorsiflexion, inversion, eversion
DTR loss: none
Lumbosacral Radiculopathy involving S1 includes:
Pain: post thigh, post calf
Sensory: postlat calf, lat foot
Weakness: hamstrings, foot plantarflex
DTR loss: Achilles
What are the peripheral neuropathy classifications?
Mononeuropathy (entrapments)
Polyneuropathy
Mononeuropathy multiplex (multiple mononeuropathy)
What’s a positive vs negative sensory sx in PNDs?
Negative: loss of sensation
Positive: paresthesias, pain (burning sensation, hyperalgesia, dysesthesia, hyperpathia)
What does dysesthesia mean? Hyperalgesia? Hyperpathia?
Dysesthesia: pain upon gentle touch
Hyperalgesia: lowered threshold to pain
Hyperpathia: pain threshold is elevated but pain is excessively felt
In PND both large and small fibers can be affected. What sensations are associated w/ these?
Large: light-touch, two-point discrimination, vibration, joint position sense
Small: temp perception, pain (pin prick)
Are fasciculations associated w/ upper or lower MN dysfunction?
Lower
Are hyperactive DTRs associated w/ central or PNS dx? Babinski sign?
CNS
CNS
What is the Babinski sign?
Stimulation of the sole of the foot w/ a sharp instrument, toes will fan and the big toe extends in positive tests (indicating a UMN lesion)
What’s a way to differentiate median n entrapment by the flexor retinaculum vs pronator teres?
Teres has an absence of nocturnal awakening
Teres involves easy fatigue of the forearm muscles
What sign may indicate anterior interosseous n (branch of median n) entrapment?
Positive OK sign where the pt is UNABLE to make the OK sign.. instead pointer and thumb cannot flex and lie flat
What are the 3 entrapments associated w/ the median n?
Carpal tunnel
Pronator syndrome
Anterior interosseous syndrome
What are sites of entrapment for the ulnar n?
Axilla
Elbow (between medial epicondyle and olecranon)
Cubital tunnel (tendinous arch of FCU)
Wrist (Guyon’s canal)
What two bones form Guyon’s canal? What n entrapment is this associated w/?
Pisiform and hamate
Ulnar
What is Froment sign? What’s it associated w/?
Pt must flex thumb to hold a piece of paper between their fingers
Ulnar n entrapment
What mm are associated w/ ulnar mononeuropathy at the elbow?
1 dorsal interosseous Abductor digiti minimi Adductor policis Flexor carpi ulnaris Flexor digitorum profundus
What two bones can the ulnar n get entrapped between in the elbow?
Medial epicondyle and olecranon
What are the 4 n entrapments associated w/ the radial n? Most common?
Axilla (Crutch Palsy)
Humerus/Spinal Groove (Saturday Night Palsy)
Supinator
Wrist
Saturday Night Palsy, goes away in a few weeks, may be confused w/ a stroke
What does humerus/spiral groove radial n entrapment (Saturday Night Palsy) cause?
Wrist drop (paresis of extensor mm of wrist, finger, and thumbs)
If a pt presents w/ foot drop, how do you differentiate between an L5 radiculopathy vs peroneal n (common fibular) entrapment?
Test inversion of the foot, if it’s..
Normal, issue w/ peroneal n
Abnormal, issue w/ L5 (peroneal n isn’t responsible for inversion of the foot)
Pt may also have back pain w/ L5, not so w/ peroneal
.. so inversion issue and back pain = L5!
A nerve conduction study would show what in its findings regarding entrapment?
Below entrapment normal findings
Above entrapment = lower conduction amplitude and decreased conduction velocity
What’s the pattern of distribution in polyneuropathy? What’s affected first/most severe?
Symmetrical in distal portion of limbs (stocking-glove)
Legs affected first
What Hereditary Motor and Sensory polyneuropathy am I supposed to remember?
Charcot-Marie-Tooth Neuropathy, T1 & 2
What kind of neuronal dx is CMT T1? T2? Which is most common?
Demyelinating
Axonal
T1
What’s the genetic transmission of CMT T1? Onset? Pt presentation?
Autosomal dominant
1st or 2nd decade
Difficulty walking/running Arreflexia Distal symmetric atrophy of legs > arms Sensory loss (mild) EMG shows slowing of motor n conduction velocities Scoliosis Hammer toes
What’s the genetic transmission of CMT T2? Onset? Pt presentation?
Autosomal dominant
Adulthood
Distal symmetric atrophy (legs > arms)
Arreflexia
Sensory loss (mild)
EMG is norm/nearly norm
What’s another name for Guillain-Barre Syndrome?
Acute inflammatory demyelinating polyneuropathy
What precedes a Guillain-Barre Syndrome?
Illness
- EBV
- Mycoplasma pneumonia
- Campylobacter jejuni
What type of weakness is associated w/ Guillain-Barre Syndrome?
Ascending symmetric
What are reflexes expected to be like in a pt w/ Guillain-Barre?
Hypo-responsive or absent
Are sensory sxs associated w/ Guillain-Barre?
No (if any, minimal)
What kind of polyneuropathy is Guillan-Barre?
Acquired acute inflammatory demyelinating
Prognosis for Guillain-Barre?
Pt likely to recover in 4-6w (up to a year or two)
25% req mech ventilator
20% experience persistent disability/fatigue
5-10% pass d/t resp failure
Tx for Guillain-Barre?
Supportive
Plasma exchange or IVIg
What lab findings are key to a Guillain-Barre diagnosis?
CSF: protein inc, glucose and cell count norm
NCV (neuronal conduction velocities): slowed, focal conduction block
What’s the variant of Guillan-Barre that often occurs in kids? What part of the body does it involve? What anti-body is diagnostic?
Miller-Fisher Syndrome
Eye muscles (ophthalmoplegia, ataxia, arreflexia, facial weakness, dysarthria, dysphagia)
GQ1b
Multifocal Motor Neuropathy has what diagnostic lab result?
Elevated serum GM-1 antibody
CSF norm
Multifocal Motor Neuropathy affects whom? What parts of the body? Are there sensory sxs or UMN signs? What’s the tx?
Adult males
Slowly progressive, hands > feet
No
IVIg
What’s the most common peripheral neuropathy identified in the US?
PN d/t DM
What cranial nerves are traditionally affected by DM?
CN III (down and out) CN VI (affected eye turns inward), CN VII
What CD4 count would someone have if a polyneuropathy were to be affecting them d/t HIV? How many pts? What kind is it?
< 200
30-50% of AIDS pts
Distal symmetrical polyneuropathy, AIDP, CIDP
What genetics are associated w/ Myasthenia Gravis?
HLA-B8
HLA-DR3
In cervical radiculopathies, roots C6-8 cause pain in the arm (at different points). What are they?
C6 = proximal arm C7 = elbow and upper forearm C8 = medial forearm
Small sensory fibers are associated w/ what?
Pain and temp
What are some causes of brachial plexopathy?
Compression/stretch (birth, CABG surgery
Inflammatory/Idiopathic (Parsonage-Turner syndrome = severe pain the shoulder)
Radiation Injury (ex: F getting tx for breast CA)
Neoplastic mass
Traumatic Injury
Ischemia (DM)
In pronator syndrome of the median n, what movement causes pain?
Forced forearm pronation
What 3 mm are associated w/ anterior interosseous syndrome?
FPL: flexor pollicus longus
FDP: flexor digitorum profundus
PQ: pronator quadratus
In anterior interosseous syndrome, what are the results expected in a NCS?
Normal
EMG is not in FPL, FDP, PQ
What EDX findings are expected in Saturday Night Palsy?
NCS normal
EMG in wrist extensors abnormal
Where is the peroneal n located?
Winds around the fibular head, hence the n’s other name common fibular
What actions are weakened by peroneal n mononeuropathies?
Foot dorsiflection
Foot eversion
Toe extension
Sensory loss to dorsum of the foot and lateral calf (winds back to L5)
What’s the most common cause of peripheral neuropathy?
DM
Regarding peripheral neuropathies, metabolic causes? Infectious causes? Immune-mediated caused? Deficiency states? Toxins? Drugs?
DM
Lyme dx, HIV
GBS, CIDP, monoclonal gammopathy (CA, multiple myeloma)
B12
Alcohol, organophosphates
Phenytoin, isoniazid (take w/ B6)
Is Charcot-Marie-Tooth a neuropathy or a myopathy? What does it kind of present as, but later on?
Neuropathy
Kinda looks like DMD, but onset is later
What deformity is seen in CMT-1?
Hammer toes
