Myopathy, Stålberg

clincial heredity

biochem MYOPATHY biopsy

Erik Stålberg

Uppsala, Sweden imaging genetics

Electrodes

A

B

C

MU

D

E

Conc EMG

signals from 2-15 muscle fibres CNEMG

• At rest denervation and spec spontaneous activity (myotonia, CRD, neuromyotonia) •MUP number of fibres in recorded area fibre diameters n-m transmission •IP recruitment pattern total number of MUs at full effort

1 Myopathy, Stålberg

Spontaneous activity Spontaneous activity from the muscle from the nerve

FINDING FINDING • fibrillation potentials, psw • neuromyotonic discharges • myotonic discharges • myokymic discharges QUANTIFY AS QUANTIFY AS • CRD • muscle cramps • #/ 10 recording sites • #/ 10 recording sites • myokymic discharges • fasciculations • myogenic extra discharges • or +, ++, +++, ++++ • neurogenic extra discharges • or +, ++, +++, ++++ – few – Few (per time unit) – moderate – moderate – abundant – abundant • or • or – spontaneous or – spontaneous or – after provocation – after provocation Stålberg Stålberg

Spontaneous acitivity generated in the muscle fibre (Stålberg,Daube 2003) Myotonic discharge Fibrillation potentials 5 ms

500 ms 100 uV

Positive waves 50 uV 5 ms

Myotonic discharges 50 ms 100 uV

100 ms 5 ms Complex repetitive discharge 100 uV

5 ms Avi 100 ms

Myotonia; warm up after 1 Myotonic discharge minute of activity

wma wma

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Myotonia; warm up after 1 minute of activity CNEMG

•At rest denervation and spec spontaneous activity (myotonia, CRD, neuromyotonia) • MUP number of fibres in recorded area fibre diameters n-m transmission •IP recruitment pattern total number of MUs at full effort

avi

MUP, normal TA MUP, myopathy TA

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Emery-Dreifuss muscular dystrophy, X-linked type 1 (EDMD; emerinopathy)

Mild to CNEMG moderate dystrophic changes: •At rest denervation and spec spontaneous Fiber size activity (myotonia, CRD, neuromyotonia) variation, a few necrotic •MUP number of fibres in recorded area fibers, central nuclei, in- fibre diameters crease of n-m transmission fibrous con- nective tissue •IP recruitment pattern and fat between total number of MUs at full effort myofibers.

Courtesy Kallimo, 2010

EMG - interference pattern Interference pattern analysis in normal, neuropathic and Myopathy myopathic conditions

Normal

Neuropathy

IP MUP

Myopathy Tib ant 18446

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CRD in Pompe´s disease (CN rec) CRD in Pompe´s disease (CN rec)

avi wma

Complex repetitive discharge, CRD Complex repetitive discharge, CRD

co-pacemaker 2 1 pacemaker 3

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Myopathy, EDB

3741

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Hereditary distal myopathy (CN rec) Muscle fibres in myopathy

normal

hypertrophy

atrophy

splitting

Recording from 2 or more still synchronous AP.s from branches of a split muscle fibre may produce high ampl Lat vastus m Stålberg

Split muscle fibers Scanning EMG

Scan in a normal muscle (simulation) Scan in a myopathic muscle (simulation)

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Scanning EMG Scanning EMG Normal Muscular dystr Normal MND

TA muscle Stålberg 0 1 mV 2 ms

Scanning EMG Scanning EMG tibial anterior muscle

mm # 7 0.7

6 0.6

5 0.5

4 0.4 normal neurogenic 3 0.3 myopathic 2 0.2

1 0.1

0 0 diameter polyph, mm # silent sect

Dioszeghy, Stålberg

EMG in general diagnostic workup in neuromuscular conditions Sensitivity/specificity of EMG in Myopathies

• Gives a quick multidimensional information about the condition • Myopathy- nmj- neuropathy •Sensitivity (abnormal vs normal): • Spontaneous activity •depends on type of myopathy: • Distribution, severity •Duchenne, myositis…….. 90-99% • Biopsy guidance •Metabolic myopathy …….may be very low

Ultrasound, CT, MRI, genetics important complements •Specificity (classification): •EMG usually not specific in separating subgroups

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EMG combined with other findings gives a clue EMG gives ”unique” information •Myopathy +Neuropathy; Fatigue: MG •think of mitochondrial dysfunction, Muscle pain: Promm (myot.+myop. in EMG) •malignancy Muscle “cramps”: EMG silent = RMD (Torbergsen) Unspec distal movements: Neuromyotonia – •Normal EMG in clinical myopathy; IBM: EMG can be performed in ”any” muscle, also where biopsy is uncommon •think of metabolic myopathy Muscle disease? EMG sometimes gives ”specific” findings (myotonia, Pompe) •Performance/EMG discrepancy; Bilat per. atrophy – CMT2? Myopati a possibility (Udd) •Weakness + full EMG pattern myopathy Dist. ext weakness – radial n.? Distal hereditary myopathy (Welander) •Weakness + normal EMG central

EMG may explain pathophysiological mechanisms

• CRD – SFEMG suggests ephaptic activation •Weakness/fatigue • Myotonic weakness – decrement of single muscle fiber aps •central • Hypokalemic paralysis – muscle fiber cond block (Zwartz) •motor neurone • Painful myot (G1306A) giant psw due to ephases in fiber groups •peripheral nerve; pnp, focal + longitud. cond block, channelopathy • Biopsy: fiber type preponderance; •muscle (nm-j, myopathy, periodic weakness) in cong. myop. - grouping? normal FD excludes reinnervation •Numbness in hypothyreosis - normal EMG = fiber type transformation •Cramps • myotonia, ben. fasc. syn., neurotonia, stiff p. syn •Pain •ICU •Critical illness…

•Weakness/fatigue •central •motor neurone •peripheral nerve; pnp, focal •muscle (nm-j, myopathy, periodic weakness)

•Cramps • myotonia, ben. fasc. syn., neurotonia, stiff p. syn •Pain •ICU •Critical illness…

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