Neuromuscular Flashcards
CMT
CMT1 (all AD) - CMT1A - duplication PMP22 (most common) - peripheral myelin protein 22-PMP22
(Vs HNPP -AD- PMP22 deletion)
-starts 10s-20s
peripheral N hypertrophy (palpable) hammertoes, high arched feet (pes cavus), ue late
NC: conduction velocity slowed no conduction block
-CMT1 and CMTX- demyelinating form
-Roussy-Levy like CMT1A+tremor+ataxia
-biopsy: onion-bulb appearance-Schwann cell proliferation (also in CIDP), not specific
CMT1B - mutation in myelin protein 0 gene
-more severe vs CMT1A
CMT demyelinating (1 and TX) - get CV and over time secondary axonal loss
axonal form - normal CV, decreased SNAP, CMAP
CMT2: axonal less severe, Sx later in life
-mitofusin2 MFM2
CMT2A2-optic atrophy
CMT2B - foot ulceration
CMT2C - diaphragm weak, VC paralysis
CMT 2D - HANDS more than feet involved
CMTX - 2nd most common-demyelinating, limited to CMT1 but X linked-males worse
-connexin 32 gene
CMT3 - Dejerine-Sottas - hypertrophic neuropathy of infancy - as infant, pain and dysesthesias, no reflexes, hypertrophy peripheral nerves
-AD or AR, multiple myeline gene mutations
CMT4 - demyelinating + axonal = RECESSIVE - rare, severe, young age, scoliosis, hearing loss + vision loss (only CMT4 AR; CMT1, FAP, HNPP, HSAN1 all AD)
CMT vs muscular dystrophy: nerve conduction different and hammertoes/high arches specific for CMT
Irregular firing pattern
Fasciculations
giant axonal neuropathy
intermediate filaments in axonal swellings
-CNS and PNS Sx
-curled hair
-walk on insides of feet
(vs metachromatic leukodystrophy-elevated urine sulfatides)
Refsum disease
AD peroxisome disorder, build up of intermediary phytanic acid build up
-retinitis pigmentosa (night blindness, VF constriction)
-hearing loss, anosmia, ataxia-cardiomyopathy
-large fiber sensorimotor neuropathy
-short 4th toe
Tx: reduce phytanic acid in diet
vs KSS - no neuropathy
Abetalipoproteinemia / Bassen-Kornzweig
AR-defect in TG transport
-DEAK deficiencies
-low serum Beta-lipoprotein + vit E
-acanthocytes
-retinitis pigmentosa, neuropathy, ataxia
-mutation in microsomal triglyceride transfer protein MTTP
Kearns Sayre syndrome
mitochondrial disease
ophthalmoplegia; oculobulbar weakness
cardiac conduction defects
retinitis, hearing loss, ataxia
NO neuropathy
Myotonic dystrophy
Autosomal dominant
DM1 DMPK (myotonic dystrophy protein kinase gene) CTG repeats on 19q; anticipation, Moderate-severe Sx age 20s-30s
“Cataracts-toupee-gonads”
-distal predominant weakness - hand and peroneal; atrophy masseters, temporalis (rare)
-laryngeal, pharyngeal muscles spared vs oculopharyngeal muscular dystrophy
-megacolon, esophageal dilation, lenticular opacities, cataracts, infertility, intellect disability
-CK slightly elevated (vs muscular dystrophy)
-EMG: myotonic discharge, early recruits MUAP, fibrillations
-histo: central nucleation, type I fiber atrophy, peripherally placed sarcoplasmic masses, ring fibers, pyknotic nuclear clumps
DM2 CNBP (cchc type nucleic acid binding protein); CCTG repeats on Zinc finger (PROMM-proximal myotonic myopathy)
protein 9 gene, no anticipation Mild-moderate Sx, average age 50
-PROXIMAL myopathy vs DM1
DM1, DM2: repeats cause sequester RNA binding proteins; causes mispliced transcripts
Sx: leg weakness, myalgia, myotonia; neck flexion weakness
Tx handgrip/oropharyngeal myotonia: mexilitine if ok for cards
Cardiac and GI muscle involved
sleep study
get lipid panel, TSH, screen for DM
-higher cancer risk
acid maltase deficiency =POMPE
ALS, MG, phrenic N injury
early respiratory muscle weakness
-orthopnea - gravity working against diaphragm
-hypoventilate daytime sleepiness, morning HA during to hypercarbia
spinobulbar muscular atrophy
gynecomastia 2/2 androgen insensitivity
central core disease
rhabdomyolysis, myoglobinuria
arsenic toxicity
red swollen feet with Mees lines (white horizontal lines on fingernails)
-hair loss
Lambert-eaton LEMS
P/Q type Ca channels Ab
Antibodies from patients with LEMS inhibit the function of the VGCCs
Autoimmune (SOX Ab negative) or paraneoplastic (SCLC) - SOX1 Ab positive
prox muscle weakness, ANS dysfxn, areflexia (vs MG)
-still need malignancy w/u; SOX antibody
-facilitation of reflexes after exercise
NC: LOW CMAP (vs MG) initally
RAPID rep stim (20-50 Hz vs MG-slow 2Hz rep stim) incremental response CMAP amplitudes
with postactivation facilitation. Decrement <10% on repetitive nerve stim increasing 100% after muscle contraction
Tx: Sx-3,4 diaminopyridine (3,4-DAP = amifampridine) blocks efflux K+ ions, prolonging depolarization, ACh exocytosis -> keep Ca channels open longer (ACHEI don’t work)
-, if severe IVIG, plasma exchange
-if autoimmune: steroids, IVIG, PLEX;
-if cancer Tx cancer and LEMS will improve
-PDE-5 inhibits for ED
botulinum
presynaptic cleavage SNARE proteins to prevent ACh release
Botulinum toxin A - SNAP-25 (snare protein)
botulinum toxin B - VAMP (snare protein)
NO sensory symptoms
2,3 HZ repetitive nerve stim - mild/moderate post-activation facilitation
neuromuscular blockers
general anesthesia
macrolide, quinolone ABx
checkpoint inhibitors
immune checkpoint inhibitor related myositis
myasthenia gravis, myositis, myocarditis, lymphopenia
-neck extensors affected, limb girdle, ocular muscle weakness
-CK not as high myositis
Tx: steroids, IVIG is refractory
antisynthetase syndrome
myositis, ILD, Anti-Jo-1, Raynaud, mechanic’s hands, arthralgias
path: perimysial fragmentation+ macrophages,
no lymphs; no capillary pathology vs dermatomyositis
immune mediated necrotizing myopathy
SRP: very high CK, evere rapid progression, rare cancer
cancer risk: if seronegative
-anti-HMG-CoA reductase IgG Ab
path: no inflammation but necrosis
dermatomyositis
anti-Mi2 nail abnormalities
highest cancer risk: TIF, NXP
anti-TIF1-gamma, anti-NXP-2 antibodies
path: capillary dropout , perifascicular atrophy (white lines around muscle fascicles) + perifascicular inflammation
-Tx: steroids, azathioprine, methotrexate (but contraindicated in ILD)
inclusion body myositis
Dx: flexors weak
early-flexor digitorum profundus weakness (forearm flexor muscle atrophy)
-quad muscle weakness
-anterior tibial muscle weakness (plantar flexion weakness)
-dysphagia
* +endomysial inflammation/rimmed vacuoles *
If histo unrevealing ->anti-NT5C1A Ab but not specific for only IBM
No Tx, does not respond to steroids
Dystrophinopathies
DMD gene mutation on X chr- largest gene, lots of spontaneous de novo mutations, deletion/duplication common
produces dystrophin protein that is dysfxnal
females rarely symptomatic - if Turner’s, uniparental disomy
female carriers - can get cardiac involvement even if no skeletal involvement, need surveillance
reading-frame rule:
in-frame mutations = milderBecker phenotype
out-of-frame predicts Duchenne
dystrophin: stabilizes membrane and protects from cell damage
Type 1 Duchenne, type 2 Becker muscular dystropy
XL recessive, most common muscle disease
1/3 caused 2/2 spontaneous mutations in dystrophin gene
Sx at young childhood, gross motor delay, toe walking
-gait: widened, equinus contracture, waddling
Limb girdle + pretibial muscles weak
Scapular winging
lumbar lordosis
cardiomyopathy
enlarged calves (+CK elevation specific to becker/duchenne) hhhghg
Duchenne - nonambulatory by 13
Becker nonambulatory by 16
CK: 5-10x elevated
path: absent dystrophin, endomysial fibrosis, fat, loss type I fibers
Tx: genetic or muscle biopsy showing no staining of dystrophin
Treat: steroids
limb girdle muscular dystrophy
AR - more common; younger onset, higher CK, more acute loss strength
AD - older, less aggressive
Facioscapulohumeral muscular dystrophy
Muscle cell death via misexpression double homeobox 4 (DUX4) - pathogenically turned on -
Fshd 1 and 2 clinically indistinguishable
-most AD
FSHD1 - 95% of pts - contraction of D4Z4 repeat array - the more contracted the worst - encodes pathologic variant - DUX4 gene turned on
-milder disease if longer repeats; short repeats have severe phenotype
facial weakness, orbicularis oculi, corners of mouth- zygomaticus major
-levator palpebrae, EOM spared
EMG - myopathic units
FSHD2 - SMCHD1 mutation - chromatin modifier genes
early Sx: signe de cils (can’t bury eyeliches), scapular winging
-Beevor sign - umbilicus moves upward with neck flexion
-dorsiflexion weakness (vs LGMD2B/R2), face is expressionless b/c weak
-CK normal or slight elevation (vs LGMDR1, scapular winging with elevated CK)
late Sx: LE weakness
EYES, EARS, LUNG (restrictive lung disease) problems
NO cardiomyopathy, no diplopia
Emery-Dreyfuss muscular dystrophy
Life threatening cardiac problems, early contractures, biceps and triceps weakness
-start adolescence
-mutation in EMD/LMNA genes
LMNA - AD
Emerin- X linked
Hypokalemia PP, hyperkalemic PP
Hyperkalemic PP - SCN4A - AD
-trigger: rest after exercise, fasting
Tx: snack, thiazide diuretic as maintenance
Hypokalemia - AD - CACNA1S most common type 1 or SCN4A (type 2)
-triggers: meals/carbs, during exercise. Tx: K sparing diuretics
-can provoke with giving glucose
Tx: carbonic anhydride inhibitors
Andersen-Tawil - KCNJ2 mutation
Steroid myopathy
CK normal, EMG nonspecific
-histo: atrophy type II fibers
Type I vs type II muscle fiber atrophy
type 1 fibers - slow oxidative,
- slow ATPase, large oxidative capacity
-red, small
2 - fast oxidative-glycolytic
-fast ATPase, large glycolytic capacity, moderate
oxidative capacity, fatigue resistant
-red, large
2b - fast oxidative-glycolytic fibers
-low oxidative capacity, fatigable
-pale, large
Type I - myotonic muscular dystrophy, nemaline, centronuclear myopathies
Type II - steroid induced myopathy
Centronuclear myopathy
- Progressive infantile
- Severe X-L neonatal - myotubular myopathy most common -
- Adult-onset
Hypotonia + ptosis , ocular palsy, bulbar weakness; can get resp failure
-CK mild elevation
EMG: myopathic pattern with sharp waves and fibrillations
Path: central nucleation, predominance type I fibers which are small and hypotropic
Vs muscular dystrophy: normal CK, no CNS involvement
X-linked myotubular myopathy -MTM1 gene
dynamin 2 (DNM2), bridging integrator 1 (amphiphysin 2) (BIN1) mutations
Myasthenia gravis
In bimodal distribution, early peak, more common in women and present earlier vs men
Not associated with HLA B27
Thyroid problems - lymphoid follicular hyperplasia
Edrophonium - increases ACh at NMJ - Tensilon test - transient improvement of weakness
-anti-striational muscle Ab positive in thymoma
-if seronegative ACh, MUSK positive in 50%
Repetitive nerve stim: 10% decrease CMAP amplitude -> if seronegative and normal repetitive nerve stim, can do single fiber EMG - most sensitive but not specific - JITTER on EMG - increase jitter/increase interpotential time
Myasthenic crisis: intubate if Nif< -30 or FVC <15 or downtrend of Nif/VC +clinic evidence resp compromise
NO: B blockers, aminoglycosides (gentamicin etc), neuromuscular blocking agents (succinylcholine)
-penicillamine - zero positive myasthenic syndrome
Thymectomy: if Sx before age 60 even if no thymoma can induce remission; myasthenic Sx can worsen peri-op - pre-op IVIG/plasma exchange
Botulinum toxin MOA
Inhibits exocytosis of presynaptic vesicles of ACh
Congenital muscular dystrophy
All: Autosomal recessive except Bethlem
-may have decreased movement in utero
- Collagenopathies -
Ullrich’s congenital muscular dystrophy-Calcanei protrusion - type VI collagen mutation
Bethlem myopathy - Autosomal dominant type VI collagen mutation - contractures elbow, ankles, hyperextend interphalangeal joints
- Merosinopathies - laminin-alpha 2 related CMD
-reduced merosin on muscle staining
-EOM spared
-intelligence normal - Dystroglycanopathies - (note dystrophin is muscular dystrophy)
muscle-eye-brain disease - muscle+brain+eye eyes less affected+less cortical change vs Walker-Warburg
Walker-Warburg - brain, eye, muscle dystrophy, elvated CK, cataract, corneal opacity
-Fukuyama: AR, fukutin mutation ; — frontal white matter changes - weakness, ocular problems , CNS abnormalities, contractures , seizures, intellectual disability
biopsy: dystrophic; reduced alpha-dystroglycan
Core myopathy
AD
Central clearing b/c no mitochondria
-RYR1 mutation
-malignant hyperthermia association
Weakness, hypotonia after birth; prox weakness
-facial, bulbar, ocular muscles spared
CK slight elevation
Oculopharyngeal muscular dystrophy
AD late onset
-dysphasia, dysarthria, ptosis, EOM involved late
-French Canadian, GCG repeat expansion in poly-A binding protein 2 gene PABP2
-biopsy: fiber size variation, rimmed vacuoles, intranuclear tubular filaments
-no myotonia, CK and aldolase normal
glycogen storage disorders
AR except phosphorylase b kinease deficiency
McArdle - myophosphorylase deficiency
Tarui - PFK deficiency
Cori - glycogenosis III-debranching enzyme deficiency; liver disease weakness adult or kid
Andersen - glycogen branching enzyme deficiency - hepatomegaly , cirrhosis, liver fail
(Von Gierke - type 1 - G6phosphatase deficiency in liver and kidney)
McArdle
glycolytic disorder (glycogenosis type V) myophosphorylase gene mutation PYGM, no glycogen to G6P ->accumulate glycogen b/c myophosphorylase deficiency
AR
-exercise induced weakness
-second wind phenomenon after rest b/c mobilize blood glucose
-physiologic muscle contractures = silent on EMG
Tarui
glycogenolytic disorder no phosphofructokinase
No G6P to G1P in muscle + RBC
-jaundice - hemolysis
-gouty arthritis (“rui” “owie “)
glycogen storage disease vs FA oxidation defect vs mitochondrial disorder
- glycogen storage -
- FA oxidation
- Mitochondrial
lysosomal storage diseases
POMPE-acid maltase deficiency - Tx alpha-glucosidase alpha - early resp muscle fail
Carotid sinus hypersensitivity
Head movement triggers-exaggerated response to baroreceptor stim
-syncope + asystole x 3 sec or fall in 50 mm Hg SBP when pressure on carotid sinus
-or hypotension without bradycardia
-reproduce Sx with carotid massage
-CN IX innervates -Nuc solitarius
Vs vasovagal: bradycardia, hypotension, triggered by neck turn
Syncope pathophysiology
- Vasovagal - inhibit vascular symathetic tone, increase vagal tone
- Carotid sinus hypersensitivity - increase parasympathetic response, reduce sympathetic tone
- 3rd ventricular tumor - colloid cyst - postural change then obstruct 3rd ventricle ->increase ICP
Glossopharyngeal neuralgia
Severe pharynx, tongue, ear pain + hypotension + bradycardia /syncope
-post traumatic or neck tumors
Adult myopathies/muscular dystrophies
Early adult onset distal myopathies:
1. Nonaka myopathy - AR distal muscle weakness LEGS first, foot drop, anterior tibial muslcle weakness, onset 20s; extensor forearm muscle weak, no proximal/bulbar involvement
GNE gene mutation = Nonaka GNAT (tubular filaments, rimmed vacuoles)
Histo: rimmed vacuoles
microscopy: tubular filaments like IBM
- Miyoshi myopathy - DYSF / dysferlin gene - AR
Dysferlin -transmembrane protein- Calcium-mediated sarcolemma resealing + repair
-[ANO5 mutation (LGMD)-anterior compartment weak]
-CK elevated, calf muscle atrophy
-DISTAL myopathy vs limb/girdle
biopsy: necrotic fibers + inflammation-
Laing myopathy - distal, anterior tibial + neck flexors then finger extensors/shoulder/hip girdle - myosin heavy chain MYH7
Late adult onset:
3. Recessive Limb Girdle Muscular Dystrophy Type 2 - DYSF mutation LGMD2B dysferlin protein (fusion/repair) - AR
-account for about a quarter of LGMD mutations
-distal localization of weakness, late onset
-shoulder girdle + hip + gastroc/plantar flexion weak
( no foot drop )-> difficulty walking UP stairs b/c can’t plantarflex ; contractures
-spares facial muscles
-absent reflexes, fatty muscle replacement
-significant elevation of CK
-biopsy: inflammation, dystrophic; NO rimmed vacuoles
-no cardiac or pulm involvement
- Markesbery-Griggs distal myopathy - AD - ZASP gene mutation; foot drop then wrist drop; late adulthood (“marcus wallberg titin with achilles foot drop, AD”) - rimmed vacuoles
- Welander - AD - onset 40-60 yrs - weak HANDS then legs (“Weleda hand cream”)
-biopsy: rimmed vacuoles - IBM - rimmed vacuole, inflammatory invasion of fibers
-NO deltoid weakness vs dermato/polymyositis
-thumb flexion weakness with interossei strong
Pyridostigmine
GI Sx side effect - muscarinic R activation
-excess dosing: cholingergic crisis, worsening weakness, respiratory involvement (wet Sx N/V/diarrhea is cholinergic crisis vs MG crisis)
-no CNS Sx, doesn’t cross BBB
-inhibits AChesterase, no destruction
Acute pandysautonomia
Orthostatic hypotension, no HR variability, anhidrosis, dry mouth, early satiety, constitution - over weeks (vs primary autonomic failure )
-Ab vs ganglionic nicotinic ACh R in 50%
-autoimmune or paraneoplastic (SCLC)
-may be triggered by illness
Tx: plasma exchange, IVIG, no full recovery
Inflammatory myopathies
- Dermatomyositis -mi2 - nail prob
TIF1y - cancer
NXP-2 - cancer
MDA-5 - ILD - Antisynthetase - AntiJo1 - mechanic’s hands, Raynaud
- Immune mediated necrotizing
SRP - aggressive , myocarditis , CK>10,000-myonecrosis but no inflammation
EMG: fibs, intertional activity, positive sharps. Tx: immunosuppression
HMG-CoA - cancer
Statin toxicity
Statin + fibrates increases risk toxicity
SLCO1B mutation associate with risk of developing statin toxicity
10x CK elevation