Electromyography (EMG) and nerve conduction studies (NCS) are useful for assessing the function of:
Electromyography and nerve conduction studies (EMG/ NCS) are useful for assessing the function of peripheral nerves. EMG records muscle activity in response to a proximal stimulation of the motor nerve. NCS record the velocity and amplitude of the nerve action potential. EMG/NCS typically is performed approximately 3 to 4 weeks after an acute injury, as nerves distal to the injury continue to transmit electrical impulses normally until degeneration of the distal nerve progresses.
The lesion that can cause mass effect and rapidly kill the patient is:
The posterior fossa (brain stem and cerebellum) requires special consideration because the volume of the posterior fossa within the cranial vault is small. Posterior fossa lesions such as tumors, hemorrhage, or stroke can cause mass effect that can rapidly kill the patient in two ways. Occlusion of the fourth ventricle can lead to acute obstructive hydrocephalus, raised intracranial pressure (ICP), herniation, and eventually death. This mass effect can also lead directly to brain stem compression (Fig. below). Symptoms of brain stem compression include hypertension, agitation, and progressive obtundation, followed rapidly by brain death. A patient exhibiting any of these symptoms needs an emergent neurosurgical evaluation for possible ventriculostomy or suboccipital craniectomy (removal of the bone covering the cerebellum). This situation is especially critical, as expeditious decompression can lead to significant functional recovery.
Maturing cerebellar stroke seen as a hypodense area in the right cerebellar hemisphere (arrowhead) on head computed tomography (CT) in a patient with rapidly progressing obtundation 2 days after the initial onset of symptoms. Swelling of the infarcted tissue causes posterior fossa mass effect. The fourth ventricle is obliterated and not visible, and the brain stem is being compressed.
According to the Glasgow Coma Scale (GCS), a patient with a head injury score of 5 is classified as:
Traumatic brain injury (TBI) can be classified as mild, moderate, or severe. For patients with a history of head trauma, classification is as follows: severe head injury if the GCS score is 3 to 8, moderate head injury if the Glasgow Coma Scale ( GCS) score is 9 to 12, and mild head injury if the GCS score is 13 to 15. Many patients present to emergency rooms and trauma bays with a history of TBI. A triage system must be used to maximize resource utilization while minimizing the chance of missing occult or progressing injuries.
In regard to the halo test, a positive indicator for cerebrospinal fluid (CFS) when tinged with blood will show the following when dropped on an absorbent tissue:
Copious clear drainage from the nose or ear makes the diagnosis of cerebrospinal fluid ( CSF) leakage obvious. Often, however, the drainage may be discolored with blood or small in volume if some drains into the throat. The halo test can help differentiate. Allow a drop of the fluid to fall on an absorbent surface such as a facial tissue. If blood is mixed with CSF, the drop will form a double ring, with a darker center spot containing blood components surrounded by a light halo of CSF. If this test is indeterminate, the fluid can be sent for beta-2 transferrin testing, a carbohydrate-free isoform of transferrin exclusively found in the CSF.
Neurapraxia is defined as:
Neurapraxia is defined as the temporary failure of nerve function without physical axonal disruption. Axon degeneration does not occur. Return of normal axonal function occurs over hours to months, often in the 2- to 4-week range.
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