A Woman With Proximal Muscle Weakness and Neuromuscular Irritability

A 67-year-old woman presented with a 6-year history of mild difficulty climbing stairs, rising from a chair, and lifting her grandchild. She denied difficulty swallowing, numbness, shortness of breath, fasciculations, or muscle stiffness. Forty years earlier, she developed mild, nonspecific cataracts. During a routine medical evaluation, she was found to have a serum creatine kinase (CK) of 1032 IU/L (normal, <200 IU/L) and was referred to a neurologist.

Her family history was positive for a grandfather diagnosed with “neuromotor ataxia,” her father had “spinal muscular atrophy,” and a brother had similar symptoms.

Her initial electrophysiologic testing (done elsewhere) demonstrated a “myopathic” EMG with polyphasic motor units and many positive sharp waves diffusely. She had an abnormal muscle biopsy that led to the diagnosis of limb-girdle dystrophy; she was then referred for evaluation at our center.

Neurologic examination revealed normal mentation and cranial nerves without ptosis, cataracts, or facial anomalies. She had more proximal than distal muscle weakness ( Fig. 111-1 ). Neck flexors were 3−/5, extensors, 4−/5; shoulder muscles, 4/5; biceps, triceps, and distal muscles were 5−/5. Distal hand muscles were normal. In the lower extremities the iliopsoas and glutei were 4/5, while the quadriceps, adductors, and distal muscles were 5/5. Reflexes were 2− and symmetrical without pathologic reflexes. There were no fasciculations or atrophy, no grip or eyelid myotonia was evident, and mild percussion myotonia was present. Sensation and coordination were normal. The rest of the examination was unremarkable.

Blood chemistry profile included normal thyroid studies and a CK of 573 IU/L (normal, <200 IU/L). No other abnormalities were detected.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Peroneal Nerve R.	Normal ≤ 5.7	Normal ≥ 3	Normal ≥ 40
Ankle	3.9	3	–
Fibular head	11.0	3	43

Median Nerve R.	Normal ≤ 4.2	Normal ≥ 6	Normal ≥ 50
Wrist	3.5	8	–
Elbow	8.7	7	50

F-Wave Studies

Nerve	Latency (ms)	Normal Latency ≤ (ms)
Peroneal nerve R.	53.6	54
Median nerve R.	28.9	30

Sensory Nerve Studies

Nerve	Onset Latency (ms)	Normal Onset Latency ≤ (ms)	Peak Latency (ms)	Normal Peak Latency ≤ (ms)	Amp (μV)	Normal Amp ≥ (μV)	Conduction Velocity (m/s)	Normal Conduction Velocity ≥ (m/s)
Sural nerve R.	3.3	3.5	3.8	4.0	13	13	42	40
Median nerve R.	2.6	2.6	3.1	3.1	25	20	50	50

EMG Data

Muscle	Insrt Activity	Fibs	Pos Waves	Fasc	Amp	Dur	Poly	Pattern
Deltoid R.	Myot	None	None	None	Dec .	Brief	Few	Full
Triceps R.	Myot	None	2+	None	Norm	Norm	Few	Full
Biceps brachii R.	Mtot	None	1+	None	Dec .	Brief	Few	Full
Pronator teres R.	Myot	None	1+	None	Norm	Norm	Few	Full
Extensor digitorum com. R.	Myot	None	1+	None	Norm	Norm	Few	Full
First dorsal interosseous R.	Myot	None	1+	None	Norm	Norm	Few	Full
Opponens pollicis R.	Myot	None	1+	None	Norm	Norm	Few	Full