Functional MRI of the cortical sensorimotor system in patients with hereditary spastic paraplegia

OBJECTIVES: The study aimed to use functional magnetic resonance imaging to ascertain changes in sensorimotor system function in patients with hereditary spastic paraplegia and to correlate it with severity of spasticity and paresis.

SETTING: Tartu University Hospital, Tartu, Estonia.

METHODS: Nine patients with autosomal-dominant pure HSP and 14 age- and sex-matched healthy controls were investigated with a 1.5T fMRI scanner during flexion/extension of the right-hand fingers and right ankle. Images were analysed with a general linear model and Statistical Parametrical Mapping software. Highest Z-scores were identified from probability maps, and weighted laterality indices were calculated using combined bootstrap/histogram analysis; these were correlated with clinical severity of spasticity and paresis.

RESULTS: During hand movements, clusters located in contralateral primary sensorimotor and premotor areas activated in both controls and patients. Bilateral activation occurred in the supplementary motor area, parietal operculum and cerebellum (predominantly ipsilateral). During the ankle task, bilateral activation was noted in the primary sensorimotor area, supplementary motor area and cerebellum. Activation clusters in HSP patients were smaller than those in controls in the sensorimotor area, especially during the ankle task, and more pronounced ipsilaterally in cerebellum both during hand and ankle motor tasks. Spasticity was significantly associated with contralateral activation in the sensory area and correlated negatively with the highest Z-scores in Brodmann areas 1-2-3 and 4.

CONCLUSION: Our results suggest changes in cortical sensorimotor network function in patients with HSP compared with healthy subjects. Lower activation in patients might reflect damage to the corticospinal tract, be influenced by compensatory mechanisms, and/or be a reflection of neurorehabilitation.