Motor neuron disease ,MND

1. Motor neuron disease ,MND zheng dongming

3. Background • The incidence of the disease is one to two per 100 000. The disease predominantly affects middle aged and elderly people.younger people are occasionally affected. • The disease is sporadic in 90% of cases, but about 10% are familial, usually with an autosomal dominant mode of inheritance.

4. The disease causes progressive injury and cell death of lower motor neurone groups in the spinal cord and brain stem and usually also of upper motor neurones in the motor cortex. • Those affected typically develop a combination of upper and lower motor neurone signs, with progressive muscle weakness and wasting usually accompanied by pathologically brisk reflexes, eventually involving the limb and bulbar muscles

5. Etiology and pathogenesis Genetics : More than 60 different mutations, mainly point mutations, have been described the most important findings has been that mutations in the gene on chromosome21 encoding the enzyme Cu/Zn superoxide dismutase (SOD1) underlie 20% of familial cases of motor neurone disease and 2% of all cases.

6. Etiology and pathogenesis Excitotoxicity: Glutamate is the main excitatory neurotransmitter in the human nervous system. Excessive stimulation of neuronal glutamate receptors can damage and kill these cells. Immune factors viral infection

7. 1.Aamyotrophic lateral sclerosis ALS • Motor neuron of Anterior horn,brain stem,pyramidal tract. • >40 years old,male>femal • weakness and wasting,The interossei and the muscles of the thenar eminence are affected early. spread proximally to involve the muscles of the shoulder girdle and thetrunk.

8. 1.Amyotrophic lateral sclerosis ALS • Fasciculation is a prominent sign. • Upper motor neuron signs in the lower limbs . There is usually a spastic weakness of the legs with increased tendon jerks and extensor plantar responses. Upper motor neuron signs may also extend to the upper limbs so that there is a paradoxical increase in the reflexes accompanying the wasting and fasciculation.

9. 1.Amyotrophic lateral sclerosis ALS • Eventuallye motor nuclei of the medulla are affected, giving rise to a bulbar palsy. Aspiration pneumonia is the most frequent cause of death. This occurs within 4-5 years of the onset of the disease in the majority of cases; some patients live for 8-10 years after the diagnosis is made. • No sense problem.

10. 2.Progressive spinal muscular atrophy ,PSMA • Anterior horne only. • <30 years old • In progressive spinal muscular atrophy, the signs of disease are limited to a lower motor neuron disorder, which often remains localized for several years. • Apart from the absence of upper motor neuron signs this form of the disease is identical with amyotrophic lateral sclerosis.

11. 3. Progressive bulbar palsy • motor nuclei of the brain-stem • The development of bulbar palsy usually results in the death of the patient within a year or two, due to aspiration pneumonia. • The ‘bulbar muscles’ may be involved in an upper motor neuron paralysis. The most striking difference is in the appearance of the tongue, which is small and stiff, instead of soft and fibrillating. The jaw jerk in this ‘pseudobulbar palsy’ is brisk.

12. 4. Primary lateral sclerosis • Pyramidal tract only • Primary lateral sclerosis is a rare sporadic disorder with exclusively upper motor neuron (UMN) involvement.

13. Assisting examination: • 1.CSF:normal • 2.EEG,CT,SEP :normal • 3.MRI:atrophy • 4.electromyography :neuropathic disorder

14. Diagnosis • progressive ,insidious, Both the upper and lower motor neurons are involved. • No disorder of sensation • Electromyography

15. Differential diagnosis • Spinal muscular atrophy SMA • Cervical vertebral disease • Syringomyelia • Benign fasciculation

16. Treatment • At present there is no curative treatment for this disease. • Riluzole is a sodium channel blocker that inhibits the release of glutamate and has several other potentially neuroprotective effects