Inpatient Video-EEG Epilepsy Monitoring

Inpatient video-EEG monitoring

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Key Diagnostic Tool for Intractable Recurrent Seizures and Unconfirmed Seizure Diagnosis

When appropriate, inpatient video-EEG monitoring offers several advantages. First, patients can safely be taken off medications that might otherwise mask seizure activity during routine EEG. Second, the studies are long enough to overcome sampling effects of shorter-duration EEG studies and the nonspecific findings and artifacts that may incorrectly suggest or refute a diagnosis of epilepsy.

For the majority of patients with epilepsy, routine electroencephalography (EEG) is sufficient to classify seizure type and initiate treatment. However, for those with intractable recurrent seizures and those with an unconfirmed seizure diagnosis, inpatient video- EEG monitoring is the best diagnostic tool available. Continuous behavioral and EEG monitoring over time in a controlled environment helps localize seizure focus, determine seizure type, and quantify the number of seizures. Equally important, video-EEG monitoring can differentiate seizures from psychologically based seizurelike episodes and from physiologic events that may be confused with epilepsy (see chart below).

Video-EEG monitoring is available at all 3 Mayo Clinic sites. Patient rooms are hard-wired with ceiling cameras for 24- hour behavioral observation and continuous EEG monitoring via external or intracranial EEG leads (eg, subdural grid or implanted depth electrodes). Other functions such as heart rate and blood pressure may be monitored as well. Monitoring may take anywhere from 24 hours to several days, depending on the number of seizures recorded in a given period of time. Patients are typically monitored long enough to capture at least 3 seizures. Digital recording allows analysis of the EEG record in a number of formats.

Upgrading Epilepsy Monitoring

Over the past few years, each Mayo Clinic campus has upgraded monitoring capacity to meet demand and improve patient experience. Mayo Clinic Arizona has expanded monitoring to 6 beds, admitting approximately 250 patients a year. Mayo Clinic Jacksonville will expand its monitoring capacity from 3 to 5 beds when the new hospital opens in April 2008. Currently, St. Luke's Hospital at Mayo Clinic Jacksonville admits approximately 120 patients per year. With 8 adult and 3 pediatric beds and the capacity to monitor in the neurology intensive care unit (ICU), Mayo Clinic Rochester can now monitor 12 patients at any one time

Adult epilepsy and pediatric epilepsy experts staff the respective monitoring units. In 2006, the Rochester units admitted 755 patients, including 236 children and 404 adults, and monitored an additional 115 patients in the ICU.

The real measure of success is not how well a patient is monitored, says Gregory D. Cascino, M.D., chair of Mayo Clinic's Division of Epilepsy, Department of Neurology, "but whether we can help patients become seizurefree or characterize clinical spells that are not epileptogenic." He likes the term "epilepsy monitoring" because at Mayo Clinic, the EEG is only one of several diagnostic tools used in the monitoring units. For example, psychiatry and dedicated neuropsychology colleagues may be on site to evaluate cognitive function and mental health of patients admitted to the monitoring unit at all Mayo Clinic campuses. Other studies, particularly for patients being considered for surgical intervention, may include a speech-language evaluation and cerebral arteriography with an intracarotid sodium amobarbital test.

Cognitive status and orientation are also monitored by nurses during and immediately after seizures. The degree of patient orientation helps establish the depth and extent of the seizure. Imaging studies using SISCOM are another aspect of inpatient epilepsy monitoring at Mayo Clinic. SISCOM stands for subtraction ictal singlephoton emission computed tomography (SPECT) coregistered to MRI. Developed at Mayo Clinic, SISCOM fuses the MRI image with the SPECT image. This recent innovation is particularly useful for localizing seizure focus in patients with intractable partial epilepsy whose MRI studies are normal. The radioactive tracer is injected by nurses immediately after a seizure. The first imaging study is performed as soon as possible and the second study within 24 hours.

Improving Diagnosis and Seizure Control

Epilepsy occurs in approximately 1% of the US population, and the elderly have one of the highest incidences of seizures and epilepsy. Joseph I. Sirven, M.D., head of the epilepsy program at Mayo Clinic Arizona, notes, "Seizures are sometimes confused with dementia, cardiac-related problems, transient ischemic attack, or other conditions of the elderly, so these patients may be under- or misdiagnosed. Seizures are considered a disease of the young, but a large portion, about one-quarter of the patients we see, are elderly."

Up to 20% of patients who are referred to comprehensive epilepsy programs with a diagnosis of intractable seizures do not have epilepsy. Jerry J. Shih, M.D., head of Mayo Clinic Jacksonville's epilepsy program, notes that particularly in the elderly, cardiac arrhythmia and vasovagal syncope may be confused with epilepsy. He explains, "Sometimes on passing out, patients with these conditions may jerk a bit or have some urinary incontinence and be somewhat disoriented when they regain consciousness. They may be given a diagnosis of seizure disorder and started on medications. Once a patient has that diagnosis, considering other diagnostic possibilities may be difficult." Video- EEG monitoring helps not only to rule out epilepsy, but also to establish the accurate diagnosis.

Inpatient video-EEG monitoring has been shown to detect previously undiagnosed seizures in up to 20% of monitored patients. As a precision tool for classifying and characterizing seizure type, it helps determine the best type of medication for the patient. In candidates for surgery, it can aid in establishing seizure locus, especially when combined with SISCOM imaging. Finally, video-EEG monitoring has been shown to improve seizure control in as many as 60% to 70% of patients.