Can you identify the cause of this patient’s progressive weakness?
A 58 year old, previously healthy, man comes to see you in clinic because of progressive left hand weakness. The exam is notable for weakness of the left thumb, and atrophy of the thenar eminence, with relative sparing of the hypothenar muscles. Your exam also reveals atrophy in the right calf, and an extensor plantar response (i.e., babinski sign) on the right.
The combination of muscle atrophy and extensor plantar response is a sign of which?
- Demyelinating disease (such as multiple sclerosis)
- A neuromuscular junction disease (such as myasthenia gravis)
- Anterior horn disease (such as ALS)
- Neuropathic disease (such as Charcot-Marie-Tooth)
Scroll down for the answer.
The answer is 3) an anterior horn disease such as Amyotrophic Lateral Sclerosis (ALS). The patient has both lower motor neuron signs (muscle atrophy) and upper motor neuron signs (the extensor plantar response), making it the most likely diagnosis of the options given.
What are the diagnostic criteria for ALS?
The criteria includes:
- Signs of lower motor neuron (LMN) degeneration by clinical, electrophysiological (EMG/NCS) or neuropathologic examination.
- Signs of upper motor neuron (UMN) degeneration by clinical examination.
- Progressive spread of signs within a region or to other regions, such as the cervical, thoracic or lumbar regions.
- No evidence of other disease that might explain the clinic symptoms.
This patient has LMN and UMN signs in two regions (lumbar and cervical) and should be evaluated for ALS, including a nerve conduction study and consideration of alternate causes of his symptoms. Note that the hemiatrophy of the hand, as described in this case, is a relatively common presenting sign of ALS.