Diagnostic Considerations
Recognition of status epilepticus (SE) may be easy or difficult. SE in the patient with sequential, generalized major motor convulsions is obvious; the patient with nonconvulsive or subtle SE presents a diagnostic dilemma.
Nonepileptic seizures (NES), formerly called psychogenic seizures, may at times be indistinguishable from generalized convulsive SE. The risk in such cases is that the physician may immediately assume that a neurologic emergency was present and embark on an aggressive course of pharmacotherapy, neglecting physical examination and historical information. [54] A brief period of observation for atypical features (see Physical Examination) may lead to the conclusion that the patient has nonepileptic seizures and does not need anticonvulsant therapy.
In one study, unresponsiveness without movement was the most common presentation of psychogenic SE. [54] Other reviews of psychogenic SE note other frequently seen presentations, including asynchronous extremity movement, forward pelvic thrusting, and geotropic eye movements (a physical finding that indicates the eyes deviating toward the ground in a nonphysiologic manner whether the head is turned left or right). [55]
A retrospective study from one institution noted that patients with psychogenic nonepileptic SE were younger, had implanted port devices for intravenous medication administration, had lower creatine kinase levels, and received higher doses of benzodiazepines compared with patients with generalized convulsive SE epilepticus. [56]
NES is associated with several behavioral characteristics that help distinguish it from a nonepileptic event. Motor activity during an NES often is punctuated by brief periods of rest, whereas epileptic convulsions are usually sustained without pause until the end of each individual seizure.
When seizure activity spreads during an epileptic seizure, it usually follows the organization of the homunculus. NES may fail to show this stereotypical and predictable evolution of behavior.
Behaviors such as pelvic thrusting, head turning from side to side, and bizarre vocalizations are usually not seen in epileptic seizures. The exception to this rule is seizure of frontal-lobe onset.
Although clinical features are usually helpful, the ultimate test to differentiate between epileptic seizures and NES is EEG.
Simple partial status epilepticus
Given the relative rarity of simple partial SE (SPSE), maintain a high degree of skepticism before considering this diagnosis. Other common processes (eg, vascular CNS insult) and other focal processes may mimic this rare entity; keep these well in mind, especially when tempted to apply increasingly risky treatment strategies. Invest more time in confirming the diagnosis and in deliberately observing the effect of each successive treatment.
The list of alternative diagnoses for SPSE is a subset of the list associated with complex partial SE (CPSE). These include the following:
-
Transient ischemia attack (TIA) and stroke
-
Migraine and its attendant neurologic phenomena (eg, sensory, visual)
-
Transient postictal phenomena analogous to Todd paresis
-
Ophthalmic disorders (eg, retinal detachment), which may mimic visual simple partial (occipital) SE
-
Peripheral neurologic syndromes and
-
Somatoform disorders
Diagnosing SPSE is understandably easiest when it arises in a patient with an established history of focal epilepsy. Evolution of SPSE from or to a clinically overt complex partial or secondarily generalized seizure also permits accurate diagnosis.
Given that confirming SPSE on clinical grounds alone may be difficult, EEG validation can be especially important. However, the yield of EEG in detecting simple partial seizure activity is variable.
Complex partial status epilepticus
CPSE is associated with more differential diagnoses than SPSE because of its variable clinical manifestations and associated altered consciousness. In addition to TIA, stroke, and migraine, other key disturbances of CNS function that mimic CPSE include toxic or metabolic encephalopathy, delirium of diverse etiologies, and transient global amnesia.
Absence SE (persistent generalized 3-Hz spike-and-wave activity) may be clinically indistinguishable from CPSE. Prolonged postictal states may closely resemble, and are more common than, CPSE.
Psychiatric causes of decreased responsiveness resembling CPSE are familiar to many tertiary epilepsy referral centers. These include severe mood disorders, psychotic disorders, and related nonepileptic phenomena (ie, pseudo-CPSE).
Periodic lateralized epileptiform discharges (PLEDs) may occur with and without focal SE. In focal SE, PLEDs may represent an ictal correlate. This interpretation is supported by an overt clinical correlate (ie, focal twitching) or by improvement in the patient's findings on neurologic examination after PLED resolution, as may occur after treatment.
However, such clinical improvement may lag the disappearance of PLEDs by hours owing to residual postictal CNS dysfunction. Marked evolution of PLEDs, such as abrupt frequency or amplitude changes, may also signify an ictal correlate. Whether the absolute discharge frequency reliably differentiates interictal from ictal PLEDs remains controversial.
Single-photon emission computed tomography (SPECT) may assist in distinguishing ictal and interictal PLEDs in the setting of possible focal SE. [57] In instances of PLEDs in focal SE, SPECT may show focal hyperperfusion. [58]
Apart from focal SE, PLEDs often represent an interictal finding associated with acute structural CNS lesions (eg, infarct, tumor, infection) or a chronic CNS lesion with a new, superimposed systemic disturbance. In this setting, PLEDs are still associated with seizures in 70-80% of cases. Both focal SE and PLEDs arise from similar clinical contexts, and both imply an increased risk of future seizures and epilepsy.
Epilepsy partialis continua
For epilepsy partialis continua (EPC), with its associated semirhythmic, repetitive muscle twitching, the differential diagnosis is a bit different from that of SPSE and CPSE. Other entities to consider include nonepileptic myoclonus, such as those of basal ganglia, brainstem, or spinal origin. The coexistence of other overt complex partial and secondarily generalized seizures and epileptiform changes in the EEG help make this distinction.
A finding of bilateral or multifocal myoclonic process argues against focal epilepsy. Multifocal myoclonus is frequently encountered in very ill, hospitalized patients, often after systemic hypoxemia, though it is occasionally related to medications or metabolic derangements.
Other movement disorders (eg, choreiform disorders, hemiballismus, tic disorders, opsoclonus-myoclonus syndrome) might theoretically be mistaken for EPC. Careful evaluation of the movements, EEG, and accompanying history may assist in differentiation. Finally, a psychogenic process may emulate EPC in rare cases.
Differential Diagnoses
-
Heatstroke
-
Hyperosmolar Hyperglycemic Nonketotic Coma
-
Hypocalcemia in Emergency Medicine
-
Neuroleptic Malignant Syndrome
-
Treatment algorithms for convulsive status epilepticus.
-
Focal status epilepticus. Electroencephalograph (EEG) in a patient with epilepsia partialis continua caused by Rasmussen encephalitis before hemispherectomy. The patient had long-standing, intractable partial epilepsy since the first decade of life. Seizures included complex partial with occasional secondary generalization and repetitive myoclonus involving the left side of the body. Note the frequent epileptiform discharges at 1-2 Hz involving the right frontocentral channels. These were evident on many of the patient's routine EEGs. Clinical myoclonus is often correlated with high-voltage bursts of such activity.
-
Focal status epilepticus. Electroencephalograph (EEG) in a 35-year-old patient with a history of intractable partial epilepsy, in complex partial status epilepticus. The patient underwent a rapid antiepileptic drug taper as an inpatient for long-term video/EEG monitoring as a presurgical candidate. On clinical observation, the patient abruptly stopped and stared, exhibiting automatisms. This first of 2 EEG fragments covers approximately 30 seconds and illustrates the start and evolution of a seizure in the right temporal lobe. The onset appears to be at Sp2 and T4. Note the time of the event, 18:35 on May 9.
-
Focal status epilepticus. This electroencephalographic (EEG) fragment was obtained at approximately 12:39 on May 10, 18 hours after the onset of complex partial status epilepticus originating in the right temporal lobe, in a 35-year-old patient with a history of intractable partial epilepsy. Other EEG acquisitions over the interval were identical. On clinical observation, the patient was lethargic, sluggish, and vague, with variable responsivity to examiners. Note the persistent epileptiform discharges at 1.5-2.5 Hz with phase reversal mainly at Sp2 though infrequently shifting to Sp1 and F7. The bulk of the discharges are maximal at Sp2, reflecting their mesial temporal origin, with rare, subtle, and low-amplitude reflection from lateral neocortical channels (F8). Background activities are slow with admixed beta frequencies. This finding corresponds to complex partial status epilepticus.
