Monomelic amyotrophy

Clinic

• MMA is a rare motor neuron disease
• It is typically marked by insidious onset of muscle atrophy of an upper limb, which plateaus after two to five years from which it neither improves nor worsens.
• There is no pain or sensory loss associated with MMA.
• MMA is not believed to be hereditary.

Symptoms

• Muscle weakness/ Atrophy esp in hand and forearm: Initially most people notice weakness in one hand. They may feel contracture of middle and ring finger and notice a thinning of the subdigital palm of the affected fingers. Progress of the condition varies, and weakness in the arm ranges from minimal to significant.
• Fasciculations: Fasciculations are uncommon (>20%)
• Tremor
• Cold hands: Increased weakness under cold conditions is commonly reported (cold paresis)
• Muscle Cramps / Sharp pains (from neck to hand)

Cause

• Impaired functioning of the anterior horn cells of the lower cervical cord (lower neck) is probable but not fully understood
• There is a debate about whether this condition represents a focal form of primary LMN degeneration or a local consequence of chronic compression from a dural expansion in the cervical spine.