41

41 CASE 41


A 19-year-old male college student is transported to the emergency department by ambulance after hitting his head in a fall from a balcony.


The student had been leaning over the balcony and fell approximately 12 feet to a carpeted floor. Witnesses indicate that he landed on his head and shoulder and immediately lost consciousness. The paramedics were called at once and, when they arrived, found the student not breathing and unresponsive to verbal commands. The patient was intubated and ventilated. His head and neck were immobilized and he was transported to the emergency department. The patient is not on any medications and has no known health problems.



PHYSICAL EXAMINATION



VS: T 34°C, P 15/min, R 10/min, BP 60/30 mm Hg

PE: Patient unresponsive, and in decerebrate posture, extension and adduction of the arms, legs and feet extended. Pupils fixed and dilated bilaterally. Glasgow Coma Scale score: 3 (severe) (normal: 15)


LABORATORY STUDIES


Radiographs of head and cervical spine: Compression fracture of the skull overlying the temporal lobe



DIAGNOSIS


Traumatic injury (coma)



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Traumatic brain injury incapacitates neuronal function at all levels. In this case, fracture of the temporal bone likely produced a tear in the middle meningeal artery of the dura. This arterial hemorrhage can produce an epidural hematoma that expands rapidly. This emergent situation, if not treated immediately, can result in herniation of the temporal lobes through the tentorial notch of the dura, resulting in pressure on the brain stem and its arterial supply and in damage to the brain stem. The lack of consciousness indicates malfunction of the cerebral cortex; the lack of breathing and the lack of eye reflexes indicates disruption of brain stem activities.


The brain stem controls the normal homeostatic functions of the body. Anatomically, it is continuous with the spinal cord and consists of the medulla oblongata, the pons, and the midbrain. The brain stem serves as a conduit for both afferent and efferent nerves that connect the spinal cord to the cortex and cerebellum. The medulla oblongata integrates many reflex activities, including coughing, gagging, swallowing, and vomiting. Nuclei in the medulla oblongata regulate autonomic nervous system output to the cardiovascular system and, along with nuclei in the pons, control respiration. The midbrain contains auditory and visual reflex centers. Interspersed among the tracts and nuclei of the brain stem are neurons that collectively are known as the ascending reticular activating system (ARAS). The function of the ARAS is to control the level of arousal and attentiveness. It participates in sleep-wake cycling. Damage to the ARAS or its blood supply will impair consciousness, and bilateral damage to this structure will result in coma. Cranial nerves III through XII exit the central nervous system at the brain stem.


Coma is a prolonged period of consciousness during which an individual does not react to external stimuli. The Glasgow Coma Scale assesses function of the eyes, response to verbal commands, and motor function as indices of neurologic function. Normal function is characterized by a Glasgow Coma Scale score of 15, and a complete lack of function is indicated by a score of 3.


Decerebrate posture indicates damage to the brain stem and results from the removal of all inhibitory descending inputs onto the spinal cord alpha-motor neurons (Fig. 41-1).


image

FIGURE 41–1 Abnormal motor activity with coma. Decorticate posturing is indicated by flexed wrist and arm and extended legs and feet. Decerebrate posturing is indicated by arm and leg extension.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 41

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