ABSTRACT
Head injury can cause temporary dysfunction (coma) or permanent lesion. Unconsciousness after cerebral injury relates to compression, hemorrhage, or ischemia. The brainstem can be displaced downwards or the temporal lobe herniates through the tentorial opening. In some comatose patients, however, there is temporary bladder retention. It is not clear whether this is related to bladder overstretching immediately after the accident or to active cerebral bladder inhibition. The possibility of temporary pontine shock similar to spinal shock cannot be excluded. In the patient with a neurologic midthoracic or higher spinal lesion, autonomic dysreflexia may occur this syndrome is secondary to loss of supraspinal inhibitory control of a thoracolumbar sympathetic outflow and results from massive discharge of the sympathetic system. Spinal cord injury to the sacral paths at S1–S4 results in parasympathetic decentralization of the bladder detrusor and somatic denervation of the external urethral sphincter, and loss of some afferent pathways.
