Page 1141 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

780 PART 6: Neurologic Disorders

much higher if a preexisting significant neurological deficit is present. above symptoms and have associated motor automatisms, such as lip
26
Factors determining outcome in SE include the type of SE, the cause, smacking or swallowing.
and the duration. In a 90-day follow-up study after convulsive SE, longer Generalized convulsive seizures are usually of the tonic-clonic type.
seizure duration, presence of cerebral insult, and progression to refrac- During the tonic phase, initial extension of the trunk is followed by
tory SE were associated with a worse outcome, only 8% of all patients extension of the arms, legs, neck, and back. The respiratory muscles
whose SE was characterized by those three factors had a good outcome, may be involved in the tonic spasm, resulting in cyanosis and decreased
as opposed to 65% of patients who had SE but none of those factors. oxygen saturation if the tonic phase is long enough, although this is rare.
21
Based on the combined assessment of previous history of seizures, The clonic phase follows and is manifest by repetitive muscle contrac-
seizure type, extent of impairment of consciousness, and age, a prognostic tions. Fixed and dilated pupils, tachycardia, and hypertension are well
score has been recently suggested for outcome prediction (STESS, status described during tonic-clonic seizures. Incontinence usually follows
epilepticus severity score). Better outcomes are observed if the status termination of the seizure. The frequency of the clonus eventually
27
is convulsive or focal, as opposed to nonconvulsive, and if the underly- wanes and respiration commences when the seizure stops. Patients may
ing etiology is epileptic or toxic. Anoxic SE, including myoclonic SE initially be deeply comatose but should begin to regain consciousness
28
following an anoxic episode carries a very poor prognosis for survival. within 15 to 20 minutes.
Survivors of SE may experience impaired cognitive function, motor Status epilepticus refers to prolonged or serial seizures without inter-
deficits, and worsening of preexisting epilepsy. Particularly, complex ictal resumption of baseline mental status. Refractory SE refers to SE
29
partial SE (CPSE) can produce limbic system damage, usually mani- that is resistant to treatment with first-line measures and requires more
fested as a memory disturbance. aggressive therapy. Super-refractory status epilepticus is refractory SE
The mortality of patients with NCSE has been reported between which is unresponsive to initial anesthetic therapy as it continues or
17% and 57%, and correlates with the underlying etiology, severity of recurs 24 hours or more after the onset of anesthesia, or on the reduction
2
impairment of mental status, and the development of acute complica- or withdrawal of anesthesia. Description of specific treatment modalities
tions (especially respiratory failure and infection). Older age had a will be reviewed below. Epilepsia partialis continua is a special type of
positive influence on outcome in one series. Causes associated with focal motor epilepsy that consists of near constant muscle contractions
17
increased mortality included anoxia, intracranial hemorrhage, tumor, of a specific muscle group. These movements can last for months or
infection, and trauma. Status epilepticus in the setting of acute isch- years without generalizing.
emic stroke has a very high mortality, approaching 35%. Prolonged There are theoretically as many different types of SE as there are sei-
30
seizure duration is a negative prognostic factor. A study of 253 adult zures, since SE is a prolonged seizure. However, SE cannot be classified
31
SE patients showed a greater than tenfold increase in mortality rate in exactly the same manner as individual seizures, because seizures are
associated with seizures lasting ≥60 minutes compared with those discrete time-limited events with symptomatology restricted to the brief
lasting 30 to 59 minutes. 32 duration of their occurrence. SE, on the other hand, can evolve over time
In children who are treated for SE in an ICU, the mortality is reported and therefore can have a symptomatology that may encompass more
close to 10%. Etiology of SE and prior neurologic abnormalities are than one seizure type. Furthermore, NCSE can have similar signs and
predictors of mortality; younger age, etiology, and duration of SE were symptoms with different EEG signatures and etiologies. The simplest
associated with morbidity. 33 classification divides SE into generalized convulsive SE and nonconvul-
sive SE, depending on whether convulsive movements are present. Since
CLASSIFICATION NCSE includes everything that is not convulsive, it describes a wide
variety of clinical entities and scenarios.
The International League Against Epilepsy’s (ILAE) classification of The conventional method of subcategorizing NCSE is to divide it into
seizures is generally accepted. The system allows classification on the absence SE and complex partial SE. This works well for patients with a
basis of clinical criteria without inferring cause. Knowledge of interictal previous history of epilepsy. In this context, absence SE denotes confu-
or ictal electroencephalographic (EEG) findings is not necessary to sion, typically mild, in a patient with generalized, approximately 3-Hz
classify seizures except for absence seizures, which are not likely to be a spike-wave discharges on EEG and a history of generalized epilepsy.
problem in the ICU. The classification system divides seizures into two Complex partial SE denotes confusion, typically waxing and waning,
types: partial, which have a focal or localized onset, and generalized, in or recurrent complex partial seizures associated with focal seizures in a
which the cortex of both cerebral hemispheres is involved simultane- patient with focal epilepsy. As defined herein, both types of NCSE imply
ously at onset. Partial seizures can further be categorized as simple, in that the encephalopathy is due to seizure activity. Historically, NCSE was
which consciousness remains intact throughout the event, or complex, labeled “absence” type if generalized EEG changes were found and “com-
in which consciousness is disrupted or altered (but not lost), often plex partial” if focal EEG changes were found, regardless of whether a
resulting in amnesia for the event. Seizures that start locally and then history of epilepsy was present.
spread to involve the entire cortex are termed secondary generalized. Many patients with NCSE do not have a history of epilepsy and
Generalized seizures are of two types: convulsive, in which tonic, clonic, do not fit into the conventional categorization elaborated above. For
or myoclonic movements are prominent, and nonconvulsive, in which a example, in a retrospective study of NCSE, we did not find any asso-
patient has an altered level of consciousness with or without very subtle ciation between EEG findings and mortality, emphasizing that this
19
motor manifestations. categorization is not very useful. This is particularly a problem in ICU
The clinical manifestation of partial seizures varies with the location patients in whom there are typically numerous factors contributing to
of their onset. Motor seizures are usually due to a lesion in the contra- encephalopathy. This nosologic uncertainty has given rise to several
lateral frontal lobe. Deviation of eyes and head toward the irritative terms to describe NCSE arising in the ICU, including ICU status, subtle
focus is often seen at the onset of seizure activity and is termed versive generalized convulsive status epilepticus, EEG status, and status in the
movement. Careful observation of the direction of this initial move- critically ill. An important aspect of ICU status is that encephalopathy
ment provides important diagnostic information regarding the location often has other causes in addition to the seizure activity.
of brain pathology. Muscle contractions may be localized to a small NCSE is of particular importance to the intensivist when it occurs
region, such as the face or fingers, or be more extensive, involving the as a sequela of inadequately treated GCSE. After prolonged generalized
entire hemibody. Movements are usually tonic or clonic, but dystonic convulsions, visible motor activity may stop, but the electrochemical
posturing is also common. Sensory seizures can be primarily auditory, seizure continues. Patients who do not start to awaken after 20 minutes
somatosensory, visual, or consist of vague visceral sensations. Patients should be assumed to have entered NCSE. NCSE following GCSE is a
with complex partial seizures may demonstrate any combination of the dangerous problem because the destructive effects of SE continue even

section06.indd 780 1/23/2015 12:55:35 PM