3nd Biennial Contemporary Clinical Neurophysiological

Symposium October 12, 2013

Abnormal Nerve Conduction Patterns

Peter D. Donofrio, M.D. Professor of Neurology

Vanderbilt University Medical Center

Diagnosis of Peripheral Neuropathy

Electrodiagnostic Tools

• Sensory nerve conduction studies • Motor nerve conduction studies and F-waves • Electromyography • Quantitative sensory testing • Autonomic reflex tests

– Quantitative sudomotor axon reflex test (QSART) – Sympathetic Skin Response – Heart rate variability, valsalva maneuver

The Motor Unit • Anterior horn cell (neuronopathy) • Motor Root (radiculopathy) • Nerve fiber (neuropathy) • Neuromuscular junction (pre/post-synaptic) • Muscle fibers (myopathy)

Patterns of Abnormalities in NCSs

• Require careful attention to: – CMAP amplitudes and distal latencies – SNAP amplitudes and distal latencies – Conduction velocities adjusted for age and

height, and especially for temperature – F-wave latencies adjusted for height – Presence of conduction block and temporal

dispersion – Temperature of the limb

Abnormal Patterns of NCSs

• Normal motor conduction studies and sensory studies – Early motor neuron disease – Mild to moderate radiculopathy – Myopathy – Myasthenia gravis – Small fiber neuropathy

Abnormal Patterns of NCSs

• Reduced CMAPS and normal sensory condition studies – Motor neuron disease – Severe radiculopathy – Motor neuropathies (Rare) – Lambert-Eaton Myasthenic Syndrome (LEMS) – Botulism – Congenital myasthenia gravis – Myopathies

Abnormal Patterns of NCSs

• Reduced or absent SNAPs, normal CMAPS – Sensory polyneuropathy – Mononeuropathy – Mononeuritis multiplex (early, sensory only) – Plexus lesion

Proposed Edx Studies in Evaluating Neuropathy

• Strategy differs depending upon severity of neuropathy by examination

Test most involved site, if mild or moderate. Test least involved site, if severe. • Peroneal motor. If no response: Tibial motor. If no peroneal or tibial responses: Peroneal motor, recording anterior tibialis. Ulnar motor. Median motor. • Sural sensory • Median sensory • Test additional nerves if finding equivocal • Definite abnormalities should result in test of: Opposite extremity. Evaluation of suspected focal abnormality. Modified from Donofrio PD, Albers JW

Motor > Sensory, Uniform Conduction

Slowing Polyneuropathy

Amiodarone Charcot-Marie-Tooth Disease Type I (Hereditary Motor Sensory

Neuropathy Type I) Cytosine arabinoside (ara-C) Dejerine-Sottas disease (Hereditary Motor Sensory Neuropathy

Type III) Doxorubicin Hexacarbon Toxicity Perhexiline maleate Sodium channel blockers

Motor > Sensory, Multifocal Conduction Slowing

Polyneuropathy Arsenic (acute intoxication) Acute Inflammatory Demyelinating Polyneuropathy (AIDP) Subacute Inflammatory Demyelinating Polyneuropathy (SIDP) Chronic inflammatory demyelinating polyneuropathy (CIDP) Chronic dysimmune polyneuropathy Monoclonal gammopathy of undetermined significance (MGUS) Osteosclerotic myeloma Multiple myeloma (substantial proportions are axonal) Waldenstrom’s macroglobulinemia Gamma heavy chain disease Castleman’s disease Lymphoma Systemic lupus erythematous Cryoglobulinemia Carcinoma HIV Multifocal motor neuropathy (MMN) with conduction block

Warmolts JR, Ann Int Med 1981

Figure 4

CIDP: Tibial Nerve

Image courtesy of P. Donofrio.

Recording Site: Abductor halluci Stimulus Site

Lat1 ms

Dur Ms

Amp mV

Area mVm

s A1: Ankle 4.9 15.9 0.9 7.6 A2: Popliteal fossa

19.1 20.00

0.5 3.1

Segment Dist mm

Diff ms

CV m/s

Temp °C

Ankle-Popliteal fossa

390 14.2 27 32.2

CIDP: Tibial F-Waves

Image courtesy of P. Donofrio.

CIDP Segmental Demyelination

Baylor College of Medicine

Multifocal Motor Neuropathy Characteristics

• Mimics ALS • Chronic Asymmetric

Distal Motor Neuropathy • Pure Motor • Arms Greater than Legs • Fasciculations, Cramps • Multifocal Conduction

Blocks on NCSs • Antibodies against GM1

ganglioside (50-80%)

Motor or Motor > Sensory, Axonal Loss

Polyneuropathy

Charcot-Marie-Tooth Disease (Hereditary Motor Sensory Neuropathy Type II) Dapsone Disulfiram Acute motor axonal neuropathy (AMAN) Acute motor sensory axonal neuropathy (AMSAN) Hyperinsulinism Nitrofurantoin, often S>M Organophosphate Poisoning Porphyria Paraneoplastic motor neuropathy (lymphoma or carcinoma)

Warmolts JR, Ann Int Med 1981

Sensory, Axonal Loss

Polyneuropathy

Carcinoma or Paraneoplastic

Cisplatin Carboplatin Oxaliplatin Congenital Metronidazole

Pyridoxine Sjögren’s syndrome Styrene Taxol Thalidomide HSN with autonomic SCAs

Paraneoplastic Sensory Neuronopathy

Sensory > Motor, Axonal Loss

Polyneuropathy Acromegaly Amyloidosis Critical illness neuropathy Connective tissue diseases Rheumatoid arthritis, SLE Periarteritis nodosa Degenerative disorders Friedreich’s ataxia, OPCA Gout Hypothyroidism Metals Arsenic (chronic) Gold, Mercury Nutritional B12 deficiency Post-gastrectomy Thiamine deficiency

Pharmaceuticals Colchicine Ethambutol Isonicotine hydrazine (INH) Nitrous oxide Phenytoin Thallium Vincristine Polycythemia vera Sarcoidosis Toxic Acrylamide Hexacarbons (glue sniffing) Organophosphorous esters Multiple myeloma Myotonic dystrophy

Sensory and Motor, Mixed conduction Slowing

and Axon-Loss Polyneuropathy

Diabetes mellitus End-stage renal disease

Axonal vs. Demyelinating

Distal Latency

Amplitude Conduction Velocity

Conduction Block

Temporal Dispersion

Axonal ↑ ↓↓ Nl or ↓ No No

Hereditary Demyelinating ↑ ↑ ↑ Nl or ↓ ↓↓↓ No No

AIDP or CIDP ↑ ↓ ↓ ↓ Yes Yes

Abnormal Patterns by Needle EMG

• Motor Neuron Disease: Abnormalities asymmetric, proximal and distal, tongue, face, SCM muscles, paraspinal muscles

• Radiculopathy: Follow a root or roots distribution • Polyneuropathy: Abnormalities, distal > proximal • NMJ: Early recruitment, may appear as a

myopathy. PSW rare, but may be seen. • Myopathy: Abnormalities: Proxmal > Distal.

Active denervation may be absent. Check paraspinals

Abnormal Patterns in Electrodiagnosis Summary

• Critical Interpretation of the CMAPs and SNAPS often gives clue to diagnosis

• Note distribution of the needle EMG abnormalities • MND is commonly asymmetric, same for radiculopathy • Neuropathies, NMJ defects and myopathies usually

symmetric • It is helpful to generate a differential diagnosis of the

electrodiagnostic findings. • State what patient has and does not have. • A great EMG report includes comments about possible

etiologies, and helps direct the referring doctor to an appropriate work up.