Which is pathgnomonic for motor neuron disease :

Answer is A (Fasciculation): Spontaneous twitchings of motor neurons or fassiculations are a characteristic feature of motor neuron disease affecting the lower motor neurons. Motor neuron disease is characterized by degeneration of motor neurons, either upper motor neuron or lower motor neuron or both. Manifestations are variable and depend on the neurons involved Upper Motor Neurons Manifestations (UMN) Coicospinal Tract Involvement (UMN of Limbs) * Hyperactive tendon reflexes Spasticity / spastic resistance to passive movements. Lower Motor Neurons Manifestations (LMN) Lower motor neurons of Limbs involved Weakness - Asymmetric - Insidious - Distal to proximal Progressive wasting and atrophy of muscles Q Fasciculations or spontaneous twitchings Coicobulbar Tract Involvement (UMN to bulbar muscles) Dysahria Exaggeration of emotion involuntary excess weeping/ laughing (pseudobulbar affect) Lower motor neurons of bulbar muscles involved Difficulty in chewing - Swallowing Movements of face and tongue