Impaired kinesthesia and cerebral integration during tendon vibration in amyotrophic lateral sclerosis.

OBJECTIVE

This study investigates the cortical processing of spindle input in patients with amyotrophic lateral sclerosis (ALS), hypothesizing that functional MRI (fMRI) activation elicited by muscle-tendon vibration would reveal specific disruptions in the integration of this sensory pathway.

METHODS

A block-designed fMRI protocol was used, consisting of 20-second periods of focal muscle-tendon vibrations (∼70-Hz frequency) applied to the first dorsal interosseous tendon, alternating with rest periods. Parametric brain activation maps were examined in 22 patients with ALS without clinically overt sensory deficits and in an age- and sex-matched group of 23 healthy controls. The relationship between task-related brain activations and clinical scores was assessed in patients reporting vibration-induced kinesthetic sensations.

RESULTS

Muscle-tendon vibration elicited activation of the precentral gyrus contralateral to the vibration site, in both ALS patients and healthy controls. Compared to controls, ALS patients exhibited reduced activation in prefrontal and cerebellar lobule VI regions. Notably, a greater proportion of ALS patients (41%) failed to perceive kinesthetic stimuli compared to controls (13%). Furthermore, activations in contralateral prefrontal and cerebellar areas were associated with hand motor disability and cognitive impairment.

CONCLUSION

It suggests that motor impairment in ALS is accompanied by disrupted perception of movement, and concomitant altered brain integration of proprioceptive inputs.

SIGNIFICANCE: ALS-related motor impairment extends beyond motor output, underscoring the need for assessing movement (body) awareness in clinical practice.