Seizure disorders and CNS infections

Epilepsy and seizure disorders

Epilepsy is a chronic brain disorder associated with abnormal electrical impulses generated by some of the neurons in the brain. These errant impulses cause seizures (Figure 20-6). A seizure is characterized by abnormalities in levels of consciousness, sensory disturbances, and impaired motor function. A diagnosis of a seizure disorder is made if the individual has two or more seizures. Children may have a single seizure associated with a high fever (i.e., febrile seizure), but that alone does not mean that the child has a seizure disorder. However, most individuals with the disorder have an onset of seizures during childhood, although many children grow out of the problem. In many cases the cause is never identified; some known causes include brain tumors, CNS infections, anoxia, CVA, and traumatic head injury.

Seizures are classified as either partial or generalized, based on how much of the brain is involved in the abnormal electrical activity. Partial seizures result from abnormal electrical activity in just one part of the brain, whereas generalized seizures involve most or all of the brain. Seizure classifications are divided into more specific categories. Simple partial seizures originate in a small, localized area of the brain, do not cause loss of consciousness, and are identified by a repetitive action, such as shaking of an arm or a leg or altered speech. Complex partial seizures also begin in a small area of the brain but cause staring and repeated movements, such as hand rubbing, lip smacking, swallowing, and postseizure confusion or amnesia. Generalized seizures include petit mal seizures, which are brief episodes characterized by staring, subtle body movement, and brief lapses of awareness.

Probably the best-known seizure disorder is the generalized tonic-clonic form that causes grand mal seizures, with loss of consciousness and tonic (stiffening) muscle contractions, followed by clonic (twitching, jerking) muscle contractions of the limbs, clenched teeth, and/or loss of bowel or bladder control. After the shaking subsides, the individual may fall asleep or appear confused for a few minutes. The patient may experience an aura, usually a sensory warning (e.g., a specific smell or taste) before a grand mal seizure.

Diagnosis depends on an accurate seizure history, EEG, and CT or MRI scans. Seizures cannot be cured but usually can be controlled effectively by pharmaceutical treatment; however, finding the most effective medication at the right dose can be complex. Depending on the seizure type, different medications are prescribed. Some individuals with epilepsy require more than one drug or have to try multiple medications until the most effective one is found. Antiseizure (anticonvulsant) medications include phenytoin (Dilantin), carbamazepine (Tegretol), valproic acid (Depakene), gabapentin (Neurontin), levetiracetam (Keppra), clonazepam (Klonopin), and lamotrigine (Lamictal). It is very important that patients know never to stop taking their seizure medication without the physician’s supervision because this may trigger more frequent and severe seizure episodes.

Central nervous system infections

Encephalitis

Most cases of encephalitis are viral in origin and are transmitted to humans from mosquitoes and ticks or are caused by other infections, such as herpes infections. In mild cases symptoms include stiff neck and headache, muscle aches, malaise, and general flulike symptoms. In more severe cases, the symptoms can include fever, delirium, seizures, coma, and even death.

Encephalitis is diagnosed by an MRI or a CT scan of the brain; lumbar puncture with CSF analysis, including cultures to determine the causative microorganism; EEG; and blood tests to detect viral antibodies. A patient with cerebral inflammation from encephalitis may suffer from confusion, disorientation, and other behavioral changes. These symptoms are part of the disease and usually disappear when the condition improves.

Patient management treats the symptoms and is aimed at controlling fever and seizure activity, in addition to constant monitoring of respiratory and urinary functions. Viral encephalitis is treated with antiviral medications, such as acyclovir (Zovirax) and foscarnet (Foscavir); if the condition is caused by herpes simplex, acyclovir (Zovirax) or ganciclovir (Cytovene) is prescribed; bacterial encephalitis is treated with antibiotics. In patients with severe CNS damage, recovery usually is prolonged, and physical therapy is necessary to overcome the neurologic and musculoskeletal complications.

Meningitis

Meningitis is an infection and inflammation of the meninges and CSF of the brain and spinal cord that can be caused by viruses, bacteria, or fungi. Meningitis is transmitted from an infected individual through coughing, sneezing, kissing, or sharing personal items, such as eating utensils or a toothbrush. Viral meningitis usually is mild and has flulike symptoms that typically resolve in about 2 weeks without treatment. Fungal meningitis is seen in patients with immune deficiencies, such as** acquired immunodeficiency syndrome (AIDS)**, and can be life-threatening. Acute bacterial meningitis can occur as a complication of an earlier infection of the ears, sinuses, or lungs, or it can be transmitted from an infected person.

Distinguishing between the types of meningitis is difficult but extremely important for effective, early treatment. Haemophilus meningitis was once the most common form of bacterial meningitis but the Haemophilus influenzae b (Hib) pediatric vaccine has greatly reduced the number of cases. Bacterial meningitis can be quite serious; symptoms include a high fever, severe headache, stiff neck, photophobia, confusion, seizures, and positive Brudzinski’s and Kernig’s signs. The diagnosis is confirmed by analysis of a CSF sample, which is tested for bacteria or blood; glucose levels (low levels occur in bacterial or fungal meningitis); and white blood cells (elevated WBCs indicate infection). The procedure is done in a hospital and takes about 45 minutes. Additional diagnostic tests include a CT scan to identify brain swelling, hemorrhage, or abscess and/or an MRI scan, which produces clearer pictures than a CT scan and can help identify brain and spinal cord inflammation and infection. The individual typically is ordered antibiotics and antiviral medications while waiting for final laboratory results because a delay in treatment can be life-threatening. The patient also is treated with analgesics and medications to reduce cerebral edema. Despite treatment, bacterial meningitis can be fatal or can cause long-term neurologic damage.