Decerebrate rigidity is characterised by all except
**Decerebrate Rigidity**
**Core Concept**
Decerebrate rigidity is a type of abnormal posturing characterized by extension of the arms and legs, typically seen in patients with severe brainstem damage or lesions. This condition is often associated with lesions affecting the midbrain or pons, leading to loss of inhibitory control over the motor neurons.
**Why the Correct Answer is Right**
Decerebrate rigidity is characterized by the following features:
- The arms are extended and internally rotated, with the elbows straight and the wrists flexed.
- The legs are extended and adducted, with the knees straight and the ankles plantarflexed.
- The patient often exhibits a "pusher" type of response, where they try to push their limbs away from the bed or examiner.
- The condition is often associated with a poor prognosis and is indicative of severe brain injury.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect because decerebrate rigidity is often seen in patients with midbrain or pons lesions, not those with cerebral cortex damage.
**Option B:** This option might be incorrect because decerebrate rigidity is not typically associated with a "decorticate" posturing, which is characterized by flexion of the arms and extension of the legs.
**Option C:** This option is likely incorrect because decerebrate rigidity is not typically seen in patients with spinal cord injuries, as the condition is a result of brainstem damage.
**Clinical Pearl / High-Yield Fact**
Decerebrate rigidity is a "red flag" for severe brain injury and requires immediate attention and investigation. It is essential to recognize this condition and differentiate it from other types of abnormal posturing, such as decorticate posturing.
**Correct Answer: D.**