It is a motor neuron disease characterized by degeneration limited to the anterior horn α motor neurons of the spinal cord. The condition features progressive muscle atrophy and weakness, typically starting in the small muscles of the hands and spreading to the entire upper and lower limbs, with loss of reflexes and no sensory disturbances.

bubble_chart Etiology

The exact cause remains unclear. Some have documented the autosomal dominant or recessive inheritance characteristics of the disease. Different cases may have various causes, such as exposure to cold, fatigue, infection, lead poisoning, trauma, and there are reports of secondary occurrences following syphilis or poliomyelitis.

bubble_chart Pathological Changes

The cervical spinal cord is most frequently affected. Degeneration of the anterior horn cells occurs, with swelling, nuclear displacement or disappearance, and gliosis, but no inflammatory reaction is seen in the anterior horn or spinal membrane, nor are there vascular changes. In some cases, the pyramidal tracts show degeneration, but pyramidal tract signs are rarely found clinically.

bubble_chart Clinical Manifestations

The onset is insidious, predominantly affecting middle-aged males. It manifests as weakness and flaccidity in hand movements, atrophy of the intrinsic hand muscles, and may present with deformities such as "claw hand" or "ape hand." Difficulties arise in buttoning clothes, picking up small objects, and writing. Subsequently, muscle weakness spreads to adjacent muscle groups, involving the arms and shoulders, and later progresses to the lower limbs. In some cases, it may start in the feet, extend to the lower limbs, and then affect the upper limbs. Muscle atrophy and weakness develop symmetrically, though sometimes only one hand is affected. Muscle tone decreases, and tendon reflexes weaken corresponding to the affected muscles. Sphincter dysfunction is absent, and pathological reflexes rarely appear, though they may be observed during frequent muscle fasciculations. Muscle fasciculations can occur in various locations and may be triggered or worsened by cold, emotional stress, or mechanical stimulation. Spontaneous pain and sensory abnormalities are absent during the course of the disease. Tongue muscle atrophy and palatal movement disorders with accompanying speech and swallowing symptoms are extremely rare.

1. CSF may show grade I protein elevation.

2. SEP test indicates the presence of vitality with normal conduction velocity.

3. EMG reveals characteristics of lower motor neuron disease.

bubble_chart Treatment Measures

There is still no specific treatment available. Amino acid preparations, nucleic acid preparations, vitamins, and vasodilators can be used. Provide a high-protein, low-fat diet and ensure adequate rest.

bubble_chart Differentiation

1. Thoracic outlet syndrome may occasionally cause symmetrical muscle atrophy in both hands, but it is often accompanied by limb pain and sensory disturbances. The muscle atrophy is limited in scope and lacks fasciculations.

2. The lateral and radicular types of cervical spondylotic myelopathy can lead to muscle atrophy in both hands, impaired fine motor skills, and weakened tendon reflexes. However, they are also frequently associated with limb pain and numbness, without fasciculations.