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Electrophysiologic evaluation of upper motor neuron involvement in amyotrophic lateral sclerosis
V E Drory1, I Kovach, G B Groozman
1Department of Neurology, ALS Clinic, Sourasky Medical Center, Tel Aviv, Israel. emgunit@tasmc.health.gov.il
Background:
The demonstration of upper motor neuron (UMN) dysfunction in patients with amyotrophic lateral sclerosis (ALS) with predominantly lower motor neuron (LMN) signs is clinically sometimes difficult.
Methods:
We analyzed the possible role of F and H waves in the diagnosis of UMN dysfunction in 36 patients with different clinical forms of ALS and 20 controls. In both lower limbs we evaluated F-wave persistence and the F/M ratio of tibial nerves, Hmax/Mmax ratio, vibratory and recurrent (paired) inhibition of the H-reflex.
Results:
The persistence of the F-response was decreased significantly in the LMN group only. The F/M amplitude ratio, vibrated-H/rest-H amplitude ratio and conditioned H/rest H amplitude ratio were significantly increased in patients with predominantly UMN, as well as in those with predominantly LMN signs. H/M amplitude ratios did not differ between the various patient groups.
Conclusion:
These findings show that ALS patients, including those without clinical evidence of UMN involvement, have a marked disinhibition of anterior horn motor neurons. The simple tests described could support an UMN abnormality when clinical signs are lacking, and help to establish a diagnosis sooner and more accurately.