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Updated: May 7, 2026
08:16
Utility of Dissociated Intrinsic Hand Muscle Atrophy in the Diagnosis of Amyotrophic Lateral Sclerosis
Published on: March 4, 2014
Cortical excitability differences in hand muscles follow a split-hand pattern in healthy controls
Parvathi Menon1, Matthew C Kiernan, Steve Vucic
1Department of Neurology, Westmead Hospital, Cnr Hawkesbury and Darcy Road, Westmead, NSW, 2145.
Muscle & Nerve
|September 17, 2013
Summary
Cortical excitability differences in healthy individuals mirror the "split-hand" pattern seen in amyotrophic lateral sclerosis. This suggests specialized hand muscle activity influences neural control.
Area of Science:
- Neuroscience
- Human Physiology
Background:
- Amyotrophic lateral sclerosis (ALS) is associated with preferential atrophy of specific intrinsic hand muscles, known as the split-hand phenomenon.
- This atrophy may stem from differences in cortical and axonal excitability.
- Investigating these excitability differences in healthy individuals can provide insights into the split-hand pattern.
Purpose of the Study:
- To determine if excitability differences follow a split-hand pattern across intrinsic hand muscles in healthy controls.
- To explore the neural underpinnings of functional hand specialization.
Main Methods:
- Threshold tracking techniques were employed to assess cortical and peripheral excitability.
- Studies were conducted on 26 healthy participants.
- Responses were recorded over the abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi muscles.
Main Results:
- Short interval intracortical inhibition was significantly greater for APB and FDI compared to other muscles.
- Motor evoked potential amplitude was larger, and the cortical silent period was longer for APB and FDI.
- At the peripheral level, the strength-duration time constant was greater when recorded over APB.
Conclusions:
- Cortical excitability differences exhibit a split-hand pattern in healthy individuals.
- This pattern may be attributed to the evolution of specialized neural control for complex hand tasks involving muscles like APB and FDI.
- Findings contribute to understanding neural adaptations in hand function.
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