Distribution of weakness in Pyrimidal tract lesions?
Ans. is 'd' i.e., Antigravity muscles are spared The following clinical features characterize a UMN lesion: Increased tone (spasticitv) Initially, UMN weakness may be flaccid, with absent or diminished deep tendon reflexes. There is little understanding of the reasons behind this initial flaccidity and it is often referred to as 'shock'. Increased tone of a UMN type is called spasticity. It may develop several hours, days or even weeks after the initial lesion has occurred. Spasticity is manifested by : Spastic catch' : Mild spasticity may be detected as a resistance to passive movement or 'catch' in the pronators on passive supination of the forearm and in the flexors of the hand/forearm on extension of the wrist/elbow. The 'clasp-knife' phenomenon: In more severe lesions, following strong resistance to passive flexion of the knee or extension of the elbow, there is a sudden relaxation of the extensor muscles of the leg and flexor muscles in the arm. Clonus: Rhythmic involuntary muscular contractions follow an abruptly applied and sustained stretch stimulus, e.g. at the ankle following sudden passive dorsiflexion of the foot. `Pyramidal-pattern' weakness The antigravity muscles are preferentially spared and stronger The flexors of the upper limbs and the extensors of the lower limbs. The patient can develop a characteristic posture of flexed and pronated arms with clenched fingers, and extended and adducted legs with plantar flexion of the feet. In upper extremiteis Relative sparing of the flexors More involvement of the extensor In lower extremities Predominant invovlement of the flexors with Relative sparing of the extensor or Absence of muscle wasting and fasciculations Focal muscle wasting andjasciculations are features of an LMN lesion. With chronic disuse, some loss of muscle bulk can occur after a UMN lesion, but this is rarely severe or focal. Brisk tendon reflexes and extensor plantar responses The tendon reflexes are brisk. The cremasteric and abdominal or 'cutaneous' reflexes are depressed or absent. The plantar responses are extensor (upgoing toes' or 'positive' babinski sign). Anti-gravity muscles are typically spared in pyramidal tract lesions. Weakness, in pyramidal tract lesions is often termed as 'pyramidal' in distribution affecting extensors more than flexors in the upper limb, and flexors more than extensors in the lower limb (Anti-gravity muscles are spared). Pyramidal weakness - Loss of power most marked in the extensors muscles in the arms and flexors in the legs Proximal weakness - Shoulders, hips, trunks, neck and sometimes face. Associated with myopathy. Distal weakness - Affects hands and feets. Associated with peripheral motor neuropathy. Global weakness - Generalized weakness in limbs which may result from severe pathologies.
Extensors more than flexors in lower limb
Flexors more than extensors in upper limb
Antigravity muscles are affected
Antigravity muscles are spared