A clinically useful definition is that a seizure cluster is
a series of seizures closely grouped in time. There are typically short (or
shorter than normal) interictal periods that often last only hours or even
minutes. Another common clinical approach is to consider clustering as an
increase over the patient's typical seizure frequency. Seizure clusters can be
experienced over a time frame as short as several minutes or as long as 1 or 2
days, as seen in women with catamenial patterns of seizures that occur
perimenstrually…
In outpatient studies to date, the prevalence of seizure
clusters varies from 13% to 76%. In inpatient studies, the range is 18% to 61%.
The higher prevalence in inpatient studies probably reflects the effect of
rapid withdrawal of antiepileptic medications in epilepsy monitoring units…
Some risk factors for seizure clusters are extratemporal
seizure onset, particularly frontal lobe onset; a history of head trauma with
loss of consciousness; longer duration of epilepsy; history of status
epilepticus; and poor seizure control. The latter risk factor, however, may be an
artifact of high seizure frequency. For patients with focal seizures, the
strongest risk factor for seizure clusters appears to be a previous experience
of clustering. Seizure clustering related to the menstrual
cycle, called catamenial epilepsy, has been described in up to 40% of women
with epilepsy.
What precipitates seizure clusters is not well understood.
In the study that used the digital seizure diary, patients were asked,
"What was the primary trigger?" each time they reported a seizure or
seizure cluster. Data about perceived precipitating factors were collected for
12,696 of the 29,341 seizures that occurred in clusters. Altogether, 28% of the seizure clusters were
attributed to sleep, waking, or sleep deprivation; 12% to mood/stress; 4% to
menstrual periods; 4% to missed medication or medication changes; 3% to medical
illness; and 1% to use of alcohol or recreational drugs. Additionally, 11% of
patients selected some other trigger, 30% said they didn't know what the trigger
was, and 6% said there was no trigger.
Seizure clusters are often treated at home with
benzodiazepines. These drugs are generally well tolerated but are not free of
adverse effects, notably sedation and risk of respiratory suppression when used
in high doses or repeatedly. In the absence
of prompt treatment, seizure clusters can evolve into status epilepticus. Even when seizure clusters don't progress,
they often lead to emergency department visits. Seizure clusters that occur in the epilepsy
monitoring unit may negatively affect the ability to locate the epileptogenic
zone, thus interfering with presurgical evaluation of patients who have
refractory epilepsy.
Seizure clustering can also be associated with postictal
psychosis. Sequelae include higher risk for recurrence of
postictal psychosis, the need for prophylactic or standing psychotropic
medication, or even psychiatric ward admission.
Most worrisome of all, seizure clustering might have a
direct effect on mortality. In a long-term observational study of
childhood-onset epilepsy in Finland (average follow-up, 37 years), the
mortality rate for patients who had seizure clusters during treatment with
antiepileptics was 42% vs 14% for patients who did not experience seizure
clusters. This finding may be confounded
by greater severity of epilepsy or higher risk of status epilepticus in patients
who experience clustering. The risk of death was not significantly
increased among patients who had clusters only prior to drug treatment…
Most respondents in all groups felt that seizure clusters
have a moderate or major negative impact on patient QoL. In fact, physicians
(80%) were significantly more likely than patients (70%) or caregivers (66%) to
have this opinion. Most patients and caregivers reported that
seizure clusters negatively affect the patient's independence, mood, and
ability to engage in normal activities…
Half of caregivers reported that the patient's seizure
clusters had a somewhat negative or very negative effect on their work. Of this
group, almost half (49%) said they sometimes had to reduce work hours or take
whole days off and 43% experienced having to stop working altogether for a
period of time. When asked to describe
how they feel when the patient experiences seizure clusters, caregivers most
frequently reported feeling stressed (67%), helpless (64%), scared (59%), and/or
overwhelmed (52%).
In certain important respects, the responses of physicians
were too optimistic when compared with those of patients or caregivers. For
example, nearly three-quarters of physicians, compared with only about half of
patients and caregivers, agreed or strongly agreed that patients with seizure
clusters can achieve a fulfilling life. Additionally, significantly fewer physicians
than patients strongly agreed that seizure clusters impede daily life. When
asked about emotional and financial burdens, significantly fewer physicians
than patients strongly agreed that there was a significant increase on
emotional and financial burden associated with seizure clusters.
Seizure clusters are associated with negative impacts on QoL
and health. Increased physician education about managing seizure clusters may
improve communication and optimize patient care by establishing an early
diagnosis of seizure clusters and then employing appropriate management
techniques. As research continues to evolve, patients will have greater options
to manage their seizure clusters. Physicians can improve seizure control and
decrease emergency facility use and thus medical costs by proactively
discussing seizure clusters with their patients and appropriately diagnosing
the clusters.
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