Epilepsy & Seizures 3 Flashcards
Evaluation of recent onset seizures and epilepsy
History
Physical and neurological examination
EEG
Neuroimaging
Other testing
Systematic approach to patients with new-onset seizure
First steps in setting the dignosis of epilepsy
1) decide whether a spell is truly epileptic or instead may be related to some other physiologic or psychogenic paroxysmal, transient phenomenon
2) decide whether an epileptic seizure was caused by an acute insult, provoked by other triggers, or related to a predisposition for recurrent, unprovoked seizures, defined as epilepsy.
Useful signs in clinical examination of new-onset seizure
The examination should assess potential injuries from a convulsive seizure such as:
tongue bites
lacerations
back pain from a compression fracture
shoulder pain from a subluxation
Blood tests in patients with new onset epilepsy
Published guidelines suggested obtaining blood glucose, blood cell counts, and electrolyte panels, particularly sodium, in specific clinical circumstances.
Toxicology screening should similarly be restricted to specific clinical circumstances
Which patients should have imaging test and which urgent imaging test
1) Patients with a first seizure should undergo neuroimaging
2) Urgent imaging should be performed in any patients with a new neurologic deficit, persistent altered mental status, recent trauma, or prolonged headache.
Which imaging test should be performed in patients with a first seizure episode
CT scan is often used as the first imaging modality because of its ease of access and should be considered for patients with new-onset seizures seen in the emergency department to assess for an acute brain insult, such as a stroke, bleed, or traumatic injury, often followed by a more accurate brain MRI performed with and without contrast
CT scans and standard MRI protocols often fail to detect the lesions associated with chronic epilepsy; for this reason, an MRI should be performed using an epilepsy-specific protocol.
Neuroimaging in chlidren with new onset epilepsy
In children with new-onset seizures, imaging may require conscious sedation or general anesthesia. An imaging study is not always required and may be omitted in children with a confident diagnosis of a benign or genetic epilepsy syndrome such as CAE or BECTS.
If there is any indication for a neuroimaging study, MRI is preferred.
Published guidelines recommend elective MRI in the presence of unexplained cognitive or motor impairment or neurological exam abnormality, partial-onset seizure, an EEG not characteristic of a benign partial epilepsy of childhood or IGE, or in children younger than 1 year of age. Emergency imaging is also recommended in any child exhibiting a prolonged postictal focal deficit
Neuroimaging in adults with new onset epilepsy
Neuroimaging is always indicated in adults with new-onset seizures or epilepsy to identify structural causes of epilepsy, some of which may require treatment of their own.
After the first unprovoked seizure, imaging in adults has a clinically significant yield of about 10%, leading to the diagnosis of disorders such as a brain tumor or other structural lesions.
CT remains the test most likely to be obtained in the emergency room after the initial seizure, but because of bone streak artifact will often miss temporal lobe pathology.
MRI is the imaging modality of choice for identifying brain pathology in patients with newonset seizures or epilepsy, and in that setting is preferably obtained with and without contrast.
What is the main contribution of routine EEG
Routine EEG is unlikely to record actual seizures, with the exception of generalized absence seizures that can be easily precipitated by hyperventilation in the untreated patient.
The main contribution of a routine EEG is the recording of interictal epileptiform activity, which includes
* spikes
* sharp waves
* spike-and-wave discharges
* polyspike-and-wave discharges
Criteria that help identify discharges as epileptiform
● They must be paroxysmal and distinct from the patient’s normal background activity.
● They must include an abrupt change in polarity occurring over several milliseconds (ms).
● The duration of each transient should be less than 200 ms. A spike has a duration of less than 70 ms; sharp waves have a duration between 70 and 200 ms.
● The discharge must have a physiologic field, with the discharge recorded from more than one electrode, and a voltage gradient should be present.
● They must not be one of the known benign variants or normal discharges such as wicket spikes, small sharp spikes (SSS), or vertex waves
EEG in absence seizures
The 3-Hz spike-and-slow-wave discharges are the hallmark of absence epilepsy. They often present in bursts lasting from 1 second to 3 seconds and can be activated by hyperventilation or hypoglycemia.
When the spike-and-slow wave discharges last longer than 6 seconds, they are often associated with an alteration of consciousness and are, thus, considered ictal discharges
EEG in juvenile myoclonic epilepsy
interictal: generalized spike-and-slow-wave discharges often occur at a faster frequency, typically from 4 Hz to 6 Hz in this syndrome.
In addition, generalized polyspikes are also seen.
Juvenile myoclonic epilepsy is often associated with a photoparoxysmal response, whereby photic stimulation can elicit a bilaterally synchronous spike and slow wave during or outlasting the photic stimulation train.
ictal: irregular 3 to 4 Hz polyspike-waves with frontocentral predominance. Jerks are usually associated with the spike component of the discharge
What is generalized paroxysmal fast activity
Generalized paroxysmal fast activity consists of bursts of generalized, sharply contoured discharges in the beta frequency range. It is more frequently observed in non rapid eye movement (REM) sleep and typically lasts from 2 seconds to 4 seconds.
Generalized paroxysmal fast activity is traditionally associated with epileptic encephalopathy with intellectual disability, such as in patients with Lennox-Gastaut syndrome, although it is also occasionally seen in individuals with generalized epilepsy and normal intelligence.
Occipital spikes: in which conditions are most commonly found and clinical features
1) Occipital spikes are frequently observed in childhood occipital epilepsy (Panayiotopoulos and Gastaut types) as well as in other types of occipital lobe epilepsy.
2) Childhood occipital epilepsy is often associated with autonomic symptoms, such as emesis, pallor, cardiorespiratory irregularities, ictal headache, and visual hallucinations
