Neurological Disorders Q 43

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A female client who was trapped inside a car for hours after a head-on collision is rushed to the emergency department with multiple injuries. During the neurologic examination, the client responds to painful stimuli with decerebrate posturing. This finding indicates damage to which part of the brain?

  

     A. Diencephalon

     B. Medulla

     C. Midbrain

     D. Cortex

    

    

Correct Answer: C. Midbrain

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Decerebrate posturing, characterized by abnormal extension in response to painful stimuli, indicates damage to the midbrain. Decerebrate posturing can be seen in patients with large bilateral forebrain lesions with progression caudally into the diencephalon and midbrain. It can also be caused by a posterior fossa lesion compressing the midbrain or rostral pons.

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Option A: Extensive lesions involving the forebrain, diencephalon, or rostral midbrain are known to cause decorticate posturing. This includes the motor cortex, premotor cortex, corona radiata, internal capsule, and thalamus. Decorticate posturing is described as abnormal flexion of the arms with the extension of the legs. Specifically, it involves slow flexion of the elbow, wrist, and fingers with adduction and internal rotation at the shoulder. The lower limbs show extension and internal rotation at the hip, with the extension of the knee and plantar flexion of the feet. Toes are typically abducted and hyperextended.

Option B: Damage to the medulla results in flaccidity. Small changes or injury to the medulla can lead to paraplegia, cardiovascular and respiratory dysfunction, or vagus nerve injury. The medulla oblongata is the connection between the brainstem and the spinal cord, carrying multiple important functional centers. It comprises the cardiovascular-respiratory regulation system, descending motor tracts, ascending sensory tracts, and origin of cranial nerves IX, X, XI, and XII.

Option D: With damage to the diencephalon or cortex, abnormal flexion (decorticate posturing) occurs when a painful stimulus is applied. Synonymous terms for decorticate posturing include abnormal flexion, decorticate rigidity, flexor posturing, or decorticate response. Brain lesions of several anatomical regions may cause both postures, though they do usually involve some degree of brainstem injury. It is, however, accepted that decorticate typically requires an injury more rostral than decerebrate posturing.

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