Altered cortical activation with finger movement after peripheral denervation: comparison of active and passive tasks

We wished to contrast cortical activation during hand movements in profoundly weak patients with motor neuropathy and in normal controls using a paradigm that is behaviourally matched between the two groups. Previous work has suggested that a passive movement task could be appropriate. Using functional magnetic resonance imaging (fMRI), we first characterised patterns of brain activation during active and passive index finger movements in healthy controls (n=10). Although the relative activation differences were highly variable, there was a trend for the mean number of significantly activated voxels in the primary motor cortex contralateral to the hand moved (CMC) to be lower for the passive than for the active task (40% relative decrease, P=0.09). There was a small posterior shift in the centre of mass of the CMC (mean, 8 mm, P<0.02) and of the ipsilateral sensorimotor cortex (IMC) (mean, 11 mm, P<0.05). No activation with passive movement was found in the patients with severe distal sensory neuropathy (n=2), suggesting that activation with passive movements is dependent on sensory feedback and unlikely to be due to mental imagery alone. In contrast, patients with severe pure motor neuropathies (MN, n=2) showed substantial increases in the volumes of activation compared to controls. The relative increases in numbers of voxels activated above threshold in different regions of interest for both the active (MN/controls: CMC, 2.1; IMC, 8.1; supplementary motor area [SMA], 5.2) and passive (CMC, 2.6; IMC, 8.0; SMA, 5.1) tasks were similar. These results confirm expansion of cortical representation for finger movement in patients with motor neuropathy and demonstrate central reorganisation as a consequence of the motor nerve loss. An expanded representation for finger movement in the primary motor cortex with peripheral weakness suggests the possibility that the primary motor cortex may encode motor unit activation rather directly. Electronic Publication     

Classification and clinical features of motor neurone diseases and motor neuropathies in adults

The term motor neurone disease encompasses combined upper and lower motor neurone disorders (amyotrophic lateral sclerosis), pure lower motor neurone disorders (spinal muscular atrophies, multifocal motor neuropathies, post irradiation lumbosacral radiculopathy, post-polio syndrome, hereditary bulbar palsy) and pure upper motor neurone disorders (primary lateral sclerosis, hereditary spastic paraplegia, neurolathyrism, Konzo). The chief clinical and electrophysiological criteria for these different disorders are discussed, with particular attention to diagnostically distinctive characteristics of each. Age of onset, and inheritance are considered as additional diagnostic features. Received: 8 July 1998 Accepted: 23 July 1998     

Microbleeds in dementia with Lewy bodies

Journal of Neurology - Microbleeds are associated with the development of dementia in older people and are common in Alzheimer’s disease (AD). Their prevalence and clinical importance in...     

Ocular palsy preceding chronic relapsing polyneuropathy by several weeks

Three patients exhibited an unusual variant of chronic relapsing polyneuritis in which extraocular muscle palsies developed 19 days, 20 days, and 3 1/2 months, respectively, before the neuropathy affected the limbs. The peripheral neuropathy evolved over 7 to 12 weeks, lasted 15 months to 13 years, and relapsed in every case. Each patient had dysphagia, areflexia, sensory loss, and weakness of all four limbs, which in two was asymmetrical. Slowed motor nerve conduction and prolonged F wave latencies were present, and the cerebrospinal fluid protein level was elevated without increased cell count. No patient recovered fully despite treatment with immunosuppressant drugs.     

DERMAL NEUROVASCULAR DYSFUNCTION IN TYPE 2 DIABETES

The present article summarizes recent observations obtained in our laboratory which clearly indicate that sex steroids exert relevant effects on the peripheral nervous system. In particular, the following important points have emerged: (1) Steroids exert stimulatory actions on the synthesis of the proteins proper of the peripheral myelin (e.g., glycoprotein Po and peripheral myelin protein 22) in vivo and on the Schwann cells in culture; (2) in many cases the actions of hormonal steroids are not due to their native molecular forms but rather to their metabolites (e.g., dihydroprogesterone and tetrahydroprogesterone in the case of progesterone; dihydrotestosterone and 5 alpha-androstane-3 alpha,17 beta -diol in the case of testosterone); (3) the mechanism of action of the various steroidal molecules may involve both classical (progesterone and androgen receptors) and nonclassical steroid receptors (GABA, receptor); and finally, (4) the stimulatory action of steroid hormones on the proteins of the peripheral myelin might have clinical significance in cases in which the rebuilding of myelin is needed (e.g., aging, peripheral injury, demyelinating diseases, and diabetic neuropathy).