A Man With Weakness and Fasciculations in the Lower Extremities

A 39-year-old black man presented with a 4-year history of pain across the lower back and legs with weakness and difficulty walking.

A previous EMG showed diffuse polyphasic motor unit potentials and fasciculations in the legs. A muscle biopsy of the right thigh showed neurogenic atrophy, and an MRI of the lumbosacral spine was reported as normal. He was referred for the evaluation for possible amyotrophic lateral sclerosis (ALS).

Past medical history was positive for traumatic fractures of the right shoulder and left foot.

He smoked 1½ packs of cigarettes per day but did not drink alcohol.

Review of systems revealed problems maintaining erections, some shortness of breath with exercise, and intermittent pain in the back and legs. He denied difficulty urinating.

Mentation and cranial nerve examination were unremarkable; in particular, there was no evidence of tongue atrophy or fasciculations. Strength in his upper extremities was normal. In the lower extremities there was 3–4/5 weakness in the foot dorsiflexors and evertors on the left leg with 5−/5 weakness of the glutei, iliopsoas, adductors, quadriceps, and hamstrings; the right hip muscles were 5−/5, other muscles were normal. Reflexes were 2+ in the upper extremities, 1 at the knees and trace at the right ankle. The ankle reflexes were absent. There were no Babinski signs. A bulbocavernous reflex could not be elicited, but the rectal examination revealed normal sphincter tone. There were no pathologic reflexes. Sensory examination was entirely normal, including the perianal area. Scattered fasciculations were detected in the legs but not in the arms. The rest of the examination was normal.

Thyroid-stimulating hormone, C3, C4, and FANA, a complete metabolic panel, and protein electrophoresis were normal. Serum creatine kinase (CK) was 663 IU/L (normal, <210 IU/L). Erythrocyte sedimentation rate was normal. A chest x-ray was normal.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site	Latency(ms)	Amplitude (mV)	Conduction Velocity (m/s)
Peroneal Nerve L.	Normal ≤ 5.7	Normal ≥ 3	Normal ≥ 40
Ankle	4.9	5	–
Fibular head	12.1	3	44

Tibial Nerve R.	Normal ≤ 5.3	Normal ≥ 4	Normal ≥ 40
Ankle	5.2	4	–
Pop. fossa	13.6	4	49

F-Wave and Tibial H-Reflex Studies

Nerve	Latency (ms)	Normal Latency ≤ (ms)
Peroneal nerve L.	52.7	54.0
Tibial nerve R.	53.8	54.0
H-reflex L.	NR	34.0
H-reflex R.	NR	34.0

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 L.	3.3	3.5	3.8	4.0	15	11	42	40

EMG Data

Muscle	Insrt Activity	Fibs	Pos Waves	Fasc	Amp	Dur	Poly	Pattern
Deltoid L.	Norm	None	None	None	Norm	Norm	Few	Full
Biceps brachii L.	Norm	None	None	None	Norm	Norm	Few	Full
1st dorsal interosseous L.	Norm	None	None	Few	Norm	Norm	Norm	Full
Gluteus medius L.	Norm	None	None	Few	Norm	Norm	Few	Full
Rectus femoris L.	Myok	Few	None	None	Norm	Norm	Norm	Red
Tibialis anterior L.	Myok	None	None	Few	Norm	Norm	Norm	Red
Peroneus longus L.	Myok	None	None	Few	Norm	Norm	Norm	Red
Gastrocnemius L.	Myok	None	None	Few	Norm	Norm	Norm	Red