Neurology India, Vol. 59, No. 5, September-October, 2011, pp. 767-768
Letter to Editor
Magnetic resonance imaging and diffusion tensor imaging in primary lateral sclerosis
Jian-Ting Qiu, Xiu-Li Shang
Department of Neurology, The First Affiliated Hospital of China Medical University, China
Primary lateral sclerosis (PLS) is a slowly progressive pure upper motor-neuron degenerative disorder of unknown etiology, and is associated with longer survival.  Recent studies suggest that magnetic resonance imaging (MRI), voxel-based diffusion tensor imaging (DTI) and tract tracking could be used to objectively document upper motor-neuron degeneration in PLS. We report the MRI and DTI features in a typical patient who met the clinical definite criteria for PLS.
A 32-year-old man presented with progressive difficulty in walking and standing up of over 3 years duration. His previous medical history was unremarkable and there was no family history of similar illness. Neurological examination revealed spasticity in all the four limbs, more so in the lower limbs, slight motor weakness in the lower limbs but no atrophy, markedly exaggerated deep tendon reflexes with bilateral Hoffmann and Babinski and spastic gait. MRI of the brain revealed hypointense signals on T1-weighted and hyperintense signals on T2-weighted sequences [Figure - 1]a limited to the bilateral symmetrical corticospinal tracts (CST) involving the subcortical white matter below the precentral gyrus, posterior limbs of the internal capsule (PLIC), cerebral peduncles, pons and medulla oblongata. DTI exhibited significantly reduced fractional anisotropy (FA) values in these regions. Besides, FA values in some other extramotor matter including genu interal capsule, body of fornix, corpus callosum were slightly lower. Furthermore, abnormally decreased color of the CST at the PLIC was observed on anisotropy map with directional color [Figure - 1]b. Diffusion tensor tractography (DTT, [Figure - 1]c and d) showed severe depletion in the CST. Electrodiagnostic studies showed lower amplitude compound motor action potentials. The patient was positive for serology of hepatitis B surface antigen and hepatitis B virus-DNA.
The existence of PLS as a distinct disease entity has been a contentious issue since its initial description.  Currently, there is no defining test or disease marker and the diagnosis is based on clinical criteria proposed by Pringle.  Previous study provided evidence that degeneration in PLS is not restricted to the upper motor neurons but also affects the lower motor neurons. However, the degree and stability of lower motor neuron involvement appears to be much less-extensive than in amyotrophic lateralizing sclerosis (ALS).  MRI, although neither sensitive nor specific for PLS, is of diagnostic valuable in PLS patients grade more than 3 disease.  DTI is an MRI technique that characterizes the diffusion properties of water molecules in vivo.  Decreased values of FA indicates axonal degeneration.  DTT is applied to reconstruct specific major white matter tract such as CST.  FA is more sensitive than DTT of the CST.  In our patient, there was extensive FA reduction of various extramotor white matter in addition to the upper motor neuron, similar to the report by Maaike.  We suggest advanced neuroimaging techniques in patients with clinical diagnosis of PLS to support the diagnosis.
Copyright 2011 - Neurology India
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