A Young Man With Large and Stiff Muscles

An 18-year-old patient had complained of muscle stiffness since he was 2½ years old, impairing his ability to exercise. He felt less stiff after warming up, and cold made the symptoms worse. His past medical history was unremarkable, and a review of systems was negative. He denied weakness or other neurologic symptoms. Family history revealed that his mother had muscle stiffness with a well-developed musculature all her life.

On examination he had normal mentation and cranial nerves, except for delayed relaxation of the orbicularis oculi muscles after forceful contraction. He was well built with prominent muscles ( Fig. 107-1 ) but had no weakness. There was delayed relaxation after a muscle contraction from gripping or percussion. Reflexes, coordination sensory tests, and the rest of the examination were normal.

Fig. 107-1

Notice patient’s prominent muscles.

What is the Most Likely Diagnosis?

The differential diagnosis of muscle enlargement includes hereditary myopathies, such as Becker’s dystrophy, and some limb-girdle dystrophies, myotonia congenita, amyloidosis, hypothyroidism, stiff-person syndrome, and parasitic infection, among others ( Table 107-1 ). Myotonic dystrophy sometimes presents initially without prominent weakness or atrophy, but those patients do not have muscle hypertrophy. Schwartz–Jampel syndrome manifests with muscle hypertrophy and myotonia, but the patient did not have the short stature or skeletal anomalies seen in this disease. The family history and early onset are against an acquired disorder of muscle irritability such as Isaacs syndrome. He had no activity-exacerbated myotonia to suggest paramyotonia congenita.

Table 107-1

Neuromuscular Causes of Muscle Hypertrophy

Adapted from Griggs R, Mendell JR, Miller RG, eds. Evaluation of the patient with myopathy. In: Evaluation and Treatment of Myopathies . Contemporary Neurology Series. Philadelphia, PA: FA Davis; 1995:26.

Generalized hypertrophy
Juvenile spinal muscular atrophy (usually early, mainly calves)
Postpolio pseudohypertrophy
Hypothyroid myopathy
Schwartz–Jampel syndrome
Isaacs syndrome
Myotonia congenita
Paramyotonia congenita
Duchenne muscular dystrophy (can be generalized but mainly in the calves)
Becker muscular dystrophy
Limb-girdle muscular dystrophy (mainly in the calves, but could be generalized in some)
Flier syndrome
Sarcoidosis (can be focal)
Parasites (cysticercosis, schistosomiasis, and trichinosis)
Focal hypertrophy
Radiculopathy of other causes of partial denervation (e.g., tethered cord)
Tendon rupture

The most likely consideration in this case with hereditary muscle hypertrophy and myotonia is myotonia congenita, Thomsen type.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site Latency (ms) Amplitude (mV) Conduction Velocity (m/s)
Median Nerve R. Normal ≤ 4.2 Normal ≥ 6 Normal ≥ 50
Wrist 3.2 15
Elbow 6.7 15 59

Peroneal Nerve R. Normal ≤ 5.7 Normal ≥ 3 Normal ≥ 40
Ankle 4.7 8
Fibular head 12.7 7 42
Knee 14.1 7 46

F-Wave Studies

Nerve Latency (ms) Normal Latency ≤ (ms)
Median nerve R. 27.8 30
Peroneal nerve R. 48.0 54

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)
Median nerve R. 2.3 2.6 2.8 3.1 35 20 57 50
Sural nerve R. 3.1 3.5 3.6 4.0 20 11 45 40

EMG Data

Muscle Insrt Activity Fibs Pos Waves Fasc Amp Dur Poly Pattern
Deltoid R. Myot None None None Norm Norm None Full
Biceps brachii R. Myot None None None Norm Norm None Full
Flexor carpi radialis R. Myot None None None Norm Norm None Full
Extensor digitorum com. R. Myot None None None Norm Norm None Full
First dorsal interosseous R. Myot None None None Norm Norm None Full
Vastus lateralis R. Myot None None None Norm Norm None Full
Tibialis anterior R. Myot None None None Norm Norm None Full
Gastrocnemius R. Myot None None None Norm Norm None Full

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Mar 25, 2024 | Posted by in NEUROLOGY | Comments Off on A Young Man With Large and Stiff Muscles

Full access? Get Clinical Tree

Get Clinical Tree app for offline access