Neuromuscular Disorders Flashcards
definition of lower motor neuron: what happens if this is messed up?
LMN: its axon and all the muscle fibers innervated by it. If there is no synchronized contraction of the muscles, weakness develops
what is the definition of the motor unit?
alpha motor neuron, the axon, and all the muscle fibers innervated
What are 3 important upper motor neuron signs?
Hyperreflexia, pathological reflexes (babinski, hoggman, clonus), spasticity
upper motor neurons are inhibitory, so if theyre damaged, you get an increase in activation
3 important lower motor neuron signs
weakness, atrophy, fasciculations
What are the 2 bulbar signs?
Dysarthria, dysphagia (speech usually first)
which motor neurons do ALS involve?
It is a multi system involvement, so the combined involvement of upper and lower motors unit injury will lead to classical features of the disease.
In terms of dx for ALS< what is the clinical presentation/course? What is supporitve lab data?
- no biomarker, no definitive radiological markers
- EMG/NCS, TMS, MRI
note: Mini-Mental State Examinations is a poor screening tool
Describe the onset of ALS
FOCAL
- limb onset (80%):
- upper: asymmetric distal (split hand
- lower: foot drop, wasting in anterior tibialis
- bulbar onset (20%)
- tongue atrophy, fasciculation
for ALS, what is the key points in differential dx?
- spinal muscular atrophy (childhood disorder, LMN only)
- Myasthenia gravis: proximal weakness, fluctuating, bulbar and eye findings, mestinon may cause fasciculations, no UMN
- cervical spondylosis: nothing above the neck
- multifocal motor neuropathy: antibody testing GM1 triad EMG
What are thre 3 ways to classify polyneuropathies (peripheral nerve)?
- FIBER INVOLVED: pure sensory, sensory motor, pure motor, autonomic
- PATHOLOGY/ELECTRODIAGNOSTIC: demyelinating, axonal, mixed
- SPEED OF PRESENTATION: acute, subacute, chronic
explain difference between mononeuropathy, mononeuritis multiplex, and polyneuropathy (peripheral neuropathy).
Mononeuropathy: pattern of weakness and sensory loss at single nerve (i.e. carpal tunnel syndrome)
Mononeuritis multiplex: multiple nerves affected in random pattern; acute onset, frequently painful (DM, vasculitis)
Polyneuropathy: distal, symmetric
What are the sensory signs of a polyneuropathy?
positve and negative symptoms?
- start in feet, move proximally
- hand symptoms appear when LE symptoms progress up to knees
- positive: pins and needles, tingling, burning
- negative: numbness, deadness, rubbery soles, “like i’m walking with thick socks on”
Describe the motor polyneuropathy symptoms
- weakness first in feet: tripping, turn ankles
- progress to weakness in hands: trouble opening jars, trouble turning key in lock
What is the most common pathophysiology of polyneuropathy
AXONAL: reflexes spared longer until muscle spindles involved; amplitude reduction on EMG
less common is demyelinating: early reflex loss
What NM disorder is a neuromuscular emergency and why?
Acute polyneuropathies (guillain barre syndrome, prphyria, toxins)
respiratory involvement, can have problems breathing
pathophysiology of Guillain Barre Syndrome and treatment (2)
immune mediated, may be post infectious (C. jejuni molecular mimicri)
treatment: plasma exchange if severe; IV immunoglobulin
5 forms of subacute polyneuropathies
1-vasculitis
2-paraneoplastic
3-chronic inflammatory demyelinating polyneuripathy
4-toxins
5-drug induced
clinical patterns: disease
acute/subacute onset
Guillan Barre syndrome, chronic inflammatory demyelinating polyneuropathy, paraneoplastic
clinical patterns: disease
proximal weakness
chronic inflammatory demyelinating polyneuropathy
clinical patterns: disease
asymmetry
vasculitis, CIDP, paraneoplastic, diabetic amyotrophy
sensory ataxia (lack of voluntary movement)
paraneoplastic, sjogrens, chronic immune sensory polyradiculopathy
clinical patterns: disease
onset in hands and feet together
CIDP, B12 deficiency
clinical patterns: diseases
small fiber, autonomic, cardiac/renal disease
DM, amyloidosis
What does DM, cancer (small cell lun ca), sjogrens, dysproteinemia, AIDS, and B12 deficiency all ahve in common regarding their neuropathies?
they are purely SENSORY
What are the 6 major neuropathies with facial nerve involvement?
1, GBS (can be bilateral)
- CIDP
- Sarcoid
- HIV
- Leprosy
What is Charcot-Marie Tooth? What is the gene?
Hereditary neuropathy: demyelinating or axonal
CMT1A: PMP22 duplication
What is the difference between Lambert-Eaton syndrome, botulism, and myasthenia gravis in terms of where the problem occurs regarding the neuromuscular junction?
LE syndrome and botulism: pre synaptic dysfunction
MG: post synaptic dysfunction
NMJ anatomy: where are the Ach receptors located? where is AchE prominent?
Receptors - at top of secondary clefts
AChE prominent in secondary clefts
In terms of release of Ach, descripte the difference between MEPP and EPP
- _small _quanta released spontaneously give rise to miniature end plate potentials
- nerve impulse AP cause huge quantal release, depolarizing the post-synaptic membrane giving rise to endplate potential
- EPP trigged excitation-contraction coupling and muscle contraction
is autonomic involved in GBS?
yes, acute.
what is the problem in lambert eaton myasthenic syndrome?
- presynaptic disorder of NMJ
- voltage gated Ca channel antibodies impede release of ach
- results in weakness, more lower extremities, autonomic involvement
what is LEMS associated with?
underlying cancer (paraneoplastic), usually small cell lung cancer
dx of MG:
most specific:
most sensitive:
specific: antibody testing
sensitive: single fiber EMG
