Reduced sensorimotor inhibition in the ipsilesional motor cortex in a patient with chronic stroke of the paramedian thalamus.
OBJECTIVE
Unilateral or bilateral paramedian infarction in the region of the thalamus and upper midbrain may lead to hypersomnia. To determine whether unilateral infarction of the paramedian thalamus leads to changes in excitability of ipsilesional primary motor hand area (M1).


METHODS
We describe a patient with chronic stroke of the right dorsomedian and intralaminar thalamic nuclei, who suffered from mild persistent hypersomnia. We studied the excitability of the right and left M1 with transcranial magnetic stimulation (TMS) in the patient, and in 10 healthy controls.


RESULTS
In contrast to healthy controls, contralateral electrical stimulation of the median nerve failed to induce short-latency afferent inhibition (SAI) in the ipsilesional M1. Other measures of corticomotor excitability and somatosensory evoked potentials were normal.


CONCLUSIONS
The selective loss of ipsilateral SAI in a patient with paramedian thalamic stroke suggests that during wakefulness, the intact paramedian thalamus facilitates the excitability of intracortical inhibitory circuits, which process thalamocortical sensory inputs in the ipsilateral M1. This preliminary finding suggests that measurements of SAI may provide a means of probing the integrity of some neural pathways, which are involved in the control of wakefulness and arousal.


CONCLUSIONS
In addition to the established role of the paramedian thalamus in arousal and memory, our observation suggests that thalamocortical projections from the paramedian thalamus contribute to the integration of sensory input at the cortical level during wakefulness.
Oliviero
A
A
FENNSI Group, Hospital Nacional de Parapléjicos, SESCAM, Finca la Peraleda s/n, Toledo, Spain. antonioo@sescam.jccm.es
León
A Molina
AM
Holler
I
I
Vila
J Florensa
JF
Siebner
H R
HR
Della Marca
G
G
Di Lazzaro
V
V
Alvarez
J Tejeira
JT
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D002908:Chronic Disease; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008475:Median Nerve / Q000503:physiopathology; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition; D013003:Somatosensory Cortex / Q000503:physiopathology*; D020521:Stroke / Q000175:diagnosis / Q000503:physiopathology*; D013786:Thalamic Diseases / Q000175:diagnosis / Q000503:physiopathology*