Upper motor neuron involvement in X-linked recessive bulbospinal muscular atrophy.
OBJECTIVE
Clinicopathological findings of X-linked recessive bulbospinal muscular atrophy (SBMA) are indicative of lower motor neuron and primary sensory neuron involvement. The aim of our study was to investigate the presence of subclinical upper motor neuron (UMN) dysfunction in this disease.


METHODS
Two siblings with clinical presentation, routine electrophysiological tests, histopathological features of muscle and nerve biopsies and genetic testing consistent with diagnosis of SBMA underwent transcranial magnetic stimulation (TMS). The analysed parameters were motor evoked potential (MEP) threshold, silent period (SP) and central motor conduction time. Intracortical inhibition with paired pulses from 1 to 6ms interstimulus intervals (ISIs) was evaluated in the older brother.


RESULTS
MEP parameters were significantly altered in limb and cranial muscles and MEP suppression after paired stimulation significantly reduced in the older brother. MEP abnormalities were present in one lower limb, but SP abolished in all limbs, in the younger brother.


CONCLUSIONS
Subclinical involvement of UMNs may be present in patients affected by SBMA. This finding suggests that the array of neuronal systems whose function may be affected by the pathogenic process of SBMA is larger than it was considered so far.


CONCLUSIONS
TMS is a sensitive diagnostic tool for the identification of UMN dysfunction and should be included in the diagnostic evaluation of patients with SBMA.
Pachatz
C
C
Clinica Neurologica, Dipartimento di Neuroscienze, Università di Roma Tor Vergata, Via Montpellier 1, 00133 Roma, Italy.
Terracciano
C
C
Desiato
M T
MT
Orlacchio
A
A
Mori
F
F
Rocchi
C
C
Bernardi
G
G
Massa
R
R
D000368:Aged; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D019054:Evoked Potentials, Motor; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology; D016472:Motor Neuron Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D009046:Motor Neurons / Q000473:pathology*; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000294:innervation / Q000473:pathology / Q000503:physiopathology; D009134:Muscular Atrophy, Spinal / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D009431:Neural Conduction; D009434:Neural Pathways / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011930:Reaction Time; D035781:Siblings; D050781:Transcranial Magnetic Stimulation