[Upper motor neuron involvement in Kennedy disease evaluated by triple stimulation technique]

Area of Science:

• Neurology
• Neurophysiology
• Genetics

Background:

• Kennedy disease (KD) is a rare genetic neuromuscular disorder.
• Upper motor neuron (UMN) dysfunction is not a primary characteristic of KD.
• Assessing subclinical UMN involvement in KD requires specialized neurophysiological tools.

Purpose of the Study:

• To investigate the presence of subclinical UMN dysfunction in KD patients.
• To evaluate the utility of the triple stimulation technique (TST) in detecting UMN abnormalities in KD.

Main Methods:

• Twenty KD patients underwent triple stimulation technique (TST), combining transcranial magnetic stimulation (TMS) with peripheral collision studies.
• TST amplitude ratio (TST test/TST control) was used to quantify motor pathway integrity.
• Electrophysiological findings and clinical signs like tendon hyperreflexia were correlated with TST results.

Main Results:

• All genetically confirmed KD patients (CAG repeat size: 44 ± 5) showed neurogenic damage on electromyography.
• TST amplitude ratio was significantly altered in 7 out of 20 KD patients.
• Abnormal TST results were observed in some patients without concurrent neurological conditions, suggesting potential UMN involvement in KD itself.

Conclusions:

• Subclinical upper motor neuron (UMN) dysfunction may be present in Kennedy disease (KD) patients.
• The triple stimulation technique (TST) shows potential for identifying UMN involvement in KD.
• It is crucial to exclude other potential causes of UMN dysfunction when evaluating KD patients.