Neuroscience Clerkship

 

 

 

 

THE EVALUATION OF NEW ONSET SEIZURES

 

The evaluation of patients with new-onset seizures is common clinical problem. These patients usually present to the emergency room, and often, little or no information is available from the patient. As the differential diagnosis is quite broad, varying from relatively benign causes to serious life threatening conditions, all patients need a thorough evaluation to determine the etiology of their seizure. Seizure is not a diagnosis per se; it is a symptoms of brain dysfunction. The underlying etiology of the seizure determines treatment, prognosis and need for further testing.
History


A careful description of the event needs to be obtained with attention to surrounding circumstances, and any evidence of aura or other preliminary symptoms (these often suggest a focal onset). As most patients are amnestic for the event, it is often important to obtain a description of the event from witnesses if possible. The patient’s past medical history is important, as are medications, any recent pregnancy, recent trauma, toxin exposure (especially alcohol or recreational drugs), symptoms of infection, or complaints of any focal neurologic deficits.


Physical Exam
 

All patients require a thorough general and neurologic physical examination. The examination should focus on any evidence of trauma, infection, and focal neurologic signs. Any fever and/or nuchal rigidity suggests CNS infection. Focal neurologic deficits may represent an old lesion, new intracranial pathology, or reversible postictal neurologic compromise (Todd's paralysis).


Laboratory studies


Patients presenting with a first time seizures require blood testing for:

Glucose

Electrolytes (including calcium and magnesium)

CBC with differential

Toxicology screen

Alcohol level

Liver and renal function tests

Lumbar puncture is required for patients in status epilepticus, or who have an unresolving post-ictal state, fever, headache, meningeal signs, a positive HIV history or who are otherwise immunocompromised.


Radiographic studies

Head CT is indicated in the acute setting of new onset seizure. CT is valuable in evaluating for possible head trauma, subarachnoid hemorrhage and mass lesions. The probability that CT imaging will be abnormal markedly increases if there is a history of recent trauma, prior stroke, or a history of malignancy.

MRI of the brain is not typically required on an emergent basis. However, if preliminary testing does not disclose an etiology for the seizure, MRI of the brain is indicated in all patients. MRI is the modality of choice to demonstrate arteriovenous malformations, neoplasm, prior stroke, congenital malformations and mesial temporal sclerosis (the latter a common cause of seizures). Imaging should be performed with gadolinium to demonstrate any vascular abnormality or neoplasm. In addition, coronal imaging with thin cuts through the temporal lobes should be performed to increase the yield of demonstrating a temporal lobe abnormality.


Electroencephahlography (EEG)

EEG is indicated in all new-onset seizure patients. It is not usually required on a stat basis unless the patient is having ongoing recurrent seizures. EEG may be able to define the location of the seizure focus. In some seizure types, the EEG can be diagnostic (e.g., primary generalized epilepsy).


Who needs to be started on an anticonvulsant and/or admitted to the hospital?

The decision to initiate anticonvulsant therapy after a single seizure is problematic. It ultimately depends on the etiology and whether there is an ongoing risk for recurrent seizures.

Take two examples on the extremes of the spectrum:

The first is a patient with a normal examination, normal imaging and normal EEG, who had a single seizure shortly after beginning a new medication known to increase the risk of seizures [e.g., wellbutrin (bupropion hydrochloride)]. In this case, there is no indication for anticonvulsant therapy.

The second is a patient with recent head trauma; a CT scan showing a small left subdural hematoma; an EEG showing ongoing spike waves in the left hemisphere; and a neurologic examination showing a subtle right hemiparesis. In this case, there is an ongoing risk for further seizures and such a patient needs to be treated with anticonvulsants.

Ultimately, it is a complex decision between the patient and the physician taking into account the likely etiology and the risk of further seizures.

Regarding the need for admission to the hospital, again this decision is complex. Clearly, any patients with new focal neurologic deficits, lesions on neuroimaging, any evidence of infection, drug intoxication or drug withdrawal, or underlying medical problems need to be admitted. More problematic is the patient with no underlying medical problems and a normal examination who recovers completely in the emergency room whose laboratory testing and CT are normal. In general, these patients can complete their evaluation as an outpatient. However, it is a decision based on the specifics of the case, made between the physician and the patient.


Important Information For Patients with New-Onset Seizures

Until their evaluation is complete, all patients with a new onset seizure must be considered at risk for future seizures. Thus, they must be directed to modify their behavior so that they would not be a danger to themselves or others if they had a recurrent seizure. This means that the physician needs to tell the patient not to drive and document this discussion in the chart. No exceptions. In additions, patients should not operate power tools, be on ladders, swim or use a bath alone. Not all contingencies can be known in advance; patients need to be told to use common sense: don’t participate in any activity which could harm themselves or others if they were to lose consciousness secondary to a seizure.