Distal hereditary motor neuropathy (dHMN) is characterized by isolated distal muscle atrophy without sensory deficit. Nevertheless, clinical sensory loss has been reported despite preserved sensory nerve conduction in a few patients, thus differentiating these cases from the classical type 2 Charcot-Marie-Tooth disease (CMT2).
We report 4 patients who presented with clinical sensory and motor neuropathy and normal peripheral sensory nerve conduction studies and were investigated with complete electrophysiological studies, including somatosensory evoked potentials (SEP).
These patients had a clinical presentation of classical CMT with isolated axonal motor neuropathy suggestive of dHMN. Interestingly, tibial nerve SEPs showed abnormalities suggestive of proximal involvement of dorsal roots that may explain the clinical somatosensory disturbances.
These cases support the concept of spinal CMT that should be recognized as an intermediate form between dHMN and CMT2. SEP recording was helpful in defining a more precise phenotype of spinal CMT.
"5.3.2. Distal hereditary motor neuropathy, spinal Charcot-Marie- Tooth disease, or distal spinal muscular atrophy Distal hereditary motor neuropathy (dHMN), also referred to as distal SMA or spinal CMT, represents a group of clinically and genetically heterogeneous diseases caused by degeneration of spinal motor neurons (Devic et al., 2012; Rossor et al., 2012). Spinal CMT is defined by a slowly progressive, symmetrical, predominantly distal lower motor neuron phenotype. "
[Show abstract][Hide abstract] ABSTRACT: Motor neuron diseases (MNDs) are an etiologically heterogeneous group of disorders of neurodegenerative origin, which result in degeneration of lower (LMNs) and/or upper motor neurons (UMNs). Neurodegenerative MNDs include pure hereditary spastic paraplegia (HSP), which involves specific degeneration of UMNs, leading to progressive spasticity of the lower limbs. In contrast, spinal muscular atrophy (SMA) involves the specific degeneration of LMNs, with symmetrical muscle weakness and atrophy. Amyotrophic lateral sclerosis (ALS), the most common adult-onset MND, is characterized by the degeneration of both UMNs and LMNs, leading to progressive muscle weakness, atrophy, and spasticity. A review of the comparative neuroanatomy of the human and zebrafish motor systems showed that, while the zebrafish was a homologous model for LMN disorders, such as SMA, it was only partially relevant in the case of UMN disorders, due to the absence of corticospinal and rubrospinal tracts in its central nervous system. Even considering the limitation of this model to fully reproduce the human UMN disorders, zebrafish offer an excellent alternative vertebrate model for the molecular and genetic dissection of MND mechanisms. Its advantages include the conservation of genome and physiological processes and applicable in vivo tools, including easy imaging, loss or gain of function methods, behavioral tests to examine changes in motor activity, and the ease of simultaneous chemical/drug testing on large numbers of animals. This facilitates the assessment of the environmental origin of MNDs, alone or in combination with genetic traits and putative modifier genes. Positive hits obtained by phenotype-based small-molecule screening using zebrafish may potentially be effective drugs for treatment of human MNDs.
Progress in Neurobiology 04/2014; 118. DOI:10.1016/j.pneurobio.2014.03.001 · 9.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This review focuses on recent advances in the diagnostic approaches and the underlying pathophysiological mechanisms of Charcot-Marie-Tooth (CMT) disease. We also discuss the emerging therapies for this hereditary neuropathy.
To date, numerous genes are implicated in CMT, and new genes have recently been found to be associated with this neuropathy (INF2, FBLN5, etc.). Some specific or evocative clinical signs of CMT subtypes (proteinuria with INF2 mutations, etc.) have been identified. Characteristic pathological findings, which may suggest gene mutations, are also recognized by nerve biopsy (mainly ultrastructural lesions).
CMT disease is the most common inherited neuromuscular disorder, with a fairly homogeneous clinical phenotype (progressive distal muscle weakness and atrophy, foot deformities, distal sensory loss, and depressed tendon reflexes). With more than 40 genes implicated, an update of the present and rather confusing classification of CMT is needed. Over the last few years, new mutated genes have been discovered. Although nerve biopsy is not routinely carried out in CMT neuropathies, it may show characteristic features, which can orientate the search for the mutated gene. There are currently no effective medications for CMT, but clinical trials are ongoing or planned.
Current opinion in neurology 08/2013; 26(5). DOI:10.1097/WCO.0b013e328364c04b · 5.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a degenerative disease which prognosis is poor. Early diagnosis permits to set up immediately adapted treatment and cares. Available diagnostic criteria are based on the detection of both the central and peripheral motor neuron injury in bulbar, cervical, thoracic and lumbar regions. Electromyographic study is the key tool to identify peripheral motor neuron involvement. Conduction velocities are systematically performed to rule out differential diagnosis. Needle examination records abnormal activities at rest and looks for neurogenic pattern during muscle contraction. Motor unit potentials morphology is modified primary to recruitment. Motor evoked potentials remain the test of choice to identify impairment of central motor neurons. For the monitoring of ALS patients, the MUNE technique (motor unit number estimation) seems the most interesting.
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