Ghost spasticity in multiple sclerosis.

Area of Science:

• Neurology
• Neurophysiology
• Rehabilitation Medicine

Background:

• Spasticity, a velocity-dependent hypertonia, is common in Upper Motor Neuron Syndrome.
• It arises from a tonic stretch reflex activated at rest.
• Understanding spasticity mechanisms in Multiple Sclerosis (MS) is crucial for patient management.

Purpose of the Study:

• To investigate hamstring stretch reflex excitability in progressive MS patients using surface electromyography (EMG).
• To correlate EMG findings with clinical assessments of spasticity and contracture.
• To identify underlying mechanisms of hamstring dysfunction in MS.

Main Methods:

• Surface electromyography (EMG) recorded biceps femoris activity in 30 progressive MS patients and 20 controls.
• Hamstrings were stretched manually at three velocities to assess phasic and tonic stretch reflexes.
• Clinical examination evaluated for hypertonia and muscle contracture.

Main Results:

• Only 7 MS patients (23%) showed clinical hamstring hypertonia; 4 had contractures.
• A tonic stretch reflex was detected in the majority of MS patients, irrespective of hypertonia.
• This suggests a prevalent subclinical hyperreflexia in MS hamstrings.

Conclusions:

• Tonic stretch reflex is common in the hamstrings of progressive MS patients, often without overt spasticity.
• This subclinical hyperreflexia, termed "ghost spasticity," is a significant risk factor for hamstring contractures.
• Early detection and management of "ghost spasticity" may prevent contracture development in MS.