AAN Guideline Reassesses the Use of Neuroimaging in the Evaluation of Seizure
Am Fam Physician. 2008 Apr 1;77(7):1024-1026.
Guideline source: Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology
Literature search described? Yes
Evidence rating system used? Yes
Published source: Neurology, October 30, 2007
Available at: http://www.neurology.org/cgi/content/full/69/18/1772
The Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (AAN) has reassessed the use of neuroimaging in patients presenting to the emergency department with seizure. Recommendations are based on 15 studies evaluated by physicians with expertise in neurology, epilepsy, neuroradiology, neurosurgery, or emergency medicine. The guideline focuses on two parameters: the effectiveness of neuroimaging as a screening tool to analyze the need for a change in acute treatment and the clinical and historical features that suggest the need for neuroimaging.
Neuroimaging to Change Acute Treatment
Change in clinical treatment is defined as the discovery of a new structural lesion or the need for surgery based on an abnormal computed tomography (CT) finding. The guideline includes the following recommendations based on the likelihood that neuroimaging will lead to treatment changes in different groups of patients (Table 1).
Table 1 Likelihood of CT Leading to a Change in Acute Treatment of Patients Presenting to the Emergency Department with Seizure
Likelihood of CT Leading to a Change in Acute Treatment of Patients Presenting to the Emergency Department with Seizure
|Patients||Number of CT scans that changed treatment/total number of CT scans (%)|
Adults with nonfebrile first seizure
Children with first seizure*
Children younger than six months with seizure
Patients with AIDS and first seizure
note: Evidence is lacking on the likelihood of neuroimaging changing treatment in patients with chronic seizures. Children with immediate posttraumatic seizure had a low rate of CT abnormalities leading to a change in treatment.
CT = computed tomography; AIDS = acquired immunodeficiency syndrome.
*— Not excluding complex febrile seizures.
ADULTS WITH FIRST SEIZURE
An emergency CT may be considered in adults with first seizure
Five studies including 98 to 875 patients with non-febrile seizure showed that, overall, CT scans in the emergency department are possibly useful in this population. In these studies, 34 to 56 percent of patients had an abnormal CT finding, including brain atrophy. Common abnormalities that led to a change in treatment included traumatic brain injury, subdural hematoma, nontraumatic bleeding, cerebrovascular accident, tumor, and brain abscess.
CHILDREN WITH FIRST SEIZURE
An emergency CT may be considered in children with first seizure.
Four studies including 25 to 475 patients with seizure (not excluding complex febrile seizures) showed that, overall, CT scans are possibly useful in this population. In these studies, 0 to 21 percent of patients had an abnormal CT finding. Common abnormalities that led to a change in treatment included cerebral hemorrhage, tumor, cysticercosis, and obstructive hydrocephalus.
PATIENTS WITH CHRONIC SEIZURE
There is no recommendation for the use of an emergency CT in patients with chronic seizure.
Evidence is lacking on the likelihood of neuroimaging changing treatment in patients with chronic seizure. However, three studies, including 60 to 139 patients with chronic seizure and 24 to 138 patients with first seizure, showed no difference between the two groups in the number of abnormal CT findings. Overall, 12 to 25 percent of patients had an abnormal CT finding. Common abnormalities included cerebral hemorrhage and shunt malfunction.
An emergency CT may be considered in children younger than six months and in patients with acquired immunodeficiency syndrome (AIDS).
Three studies included a special population (i.e., age younger than six months, immediate posttraumatic seizure, or AIDS). Children younger than six months with seizure and patients with AIDS and first seizure had high rates of abnormalities on CT; therefore, CT scans are possibly useful in these populations. Children with immediate posttraumatic seizure had a low rate of CT abnormalities leading to a change in treatment. Common abnormalities in children younger than six months included Aicardi's syndrome, Miller-Dieker syndrome, tuberous sclerosis, infarction, and depressed skull fracture. Central nervous system toxoplasmosis was common in patients with AIDS.
Features Suggesting the Need for Neuroimaging
An emergency CT should be considered in patients presenting to the emergency department with seizure who have an abnormal neurologic examination, a predisposing history, or focal onset of seizure.
The evaluation of features associated with abnormal CT findings focused on any abnormality, not just those that led to a change in treatment. An analysis of nine studies identified several features associated with neuroimaging (Table 2). Multiple studies showed that a focal abnormality on neurologic examination, a predisposing history, or focal onset of seizure is associated with abnormal findings.
Table 2 Factors Associated with Abnormal CT Findings in Patients Presenting to the Emergency Department with Seizure
Factors Associated with Abnormal CT Findings in Patients Presenting to the Emergency Department with Seizure
Focal abnormality on neurologic examination
Focal onset of seizure
Absence of a history of alcohol abuse
History of cysticercosis
Patient older than 65 years
Seizure duration of more than 15 minutes
CT = computed tomography.
*— Age younger than six months, closed head injury, recent cerebrospinal fluid shunt revision, malignancy, neurocutaneous disorders.
The evidence does not support strong recommendations because many of the studies analyzed did not mask the clinical presentation and included varying patient populations. None of the studies included good data on the use of magnetic resonance imaging (MRI); therefore, no recommendations could be made. Future research should address the emergent use of MRI in patients presenting to the emergency department with seizure because MRI may be more sensitive than CT for detecting brain pathology underlying seizure disorders.
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