EEG & Sleep
A 3-Hz spike-and-wave EEG pattern is characteristic of which seizure type?
Absence seizures (also known as petit mal seizures)
Key features include brief loss of awareness, subtle blinking/mouth movements, no postictal state. Patient does not recall anything. It's almost as if they just lost time.
3 Hz spike is due to thalamic neuron hyperpolarization.
This seizure involves lip-smacking and altered awareness
Complex partial seizure / Focal impaired awareness seizure
Sometimes, Absence seizures as well.
What environmental factor commonly provokes seizures in alcoholics?
Alcohol withdrawal
Alcohol use causes tolerance of the GABA receptors. Predisposes patients to seizures during withdrawal.
Other substances can also precipitate seizures i.e. antipsychotics, antidepressants, narcotics, etc.
What's the first-line treatment for absence seizures?
Ethosuximide
Second line - broad-spectrums like levitiracetam/lamotrigine
DON'T USE NARROW-SPECTRUM like carbamazepine, they can worsen generalized seizures such as absence seizures.
What is the most important first step during an active seizure?
Ensure airway, breathing, and circulation.
Patient loses voluntary control of muscles and airway. At risk for hypoxia, aspiration, and trauma!
What type of brain activity does an EEG measure?
Postsynaptic potentials from cortical (surface) neurons.
The voltage is the summation of many, many neurons.
This seizure causes sudden muscle loss ("drop attacks").
Atonic seizure
This genetic syndrome presents with seizures, intellectual disability, and a "happy" demeanor.
Angelman syndrome
Angelman syndrome is caused by loss of the maternal UBE3A gene on 15q11–q13.
Because the paternal copy is imprinted, neurons lose all UBE3A expression. This leads to impaired synaptic protein degradation, disrupted GABAergic balance, and epilepsy in ~85% of patients (onset 1–3 years).
What's the mechanism for ethosuximide?
Blocks T-type calcium channels in thalamic neurons.
EFG HIJ mnemonic for side effects:
E - ethosuximide, F - fatigue, G - GI distress, H - headache, I - itching, J - joint pain
Name one of the two most common causes of breakthrough seizures?
Medication nonadherence and/or sleep deprivation.
Sleep deprivation can pre-dispose to seizures! Healthy sleep schedule is one of the hallmarks of lifestyle changes suggested to patients.
Some studies show cortical hyperexcitability (decreased GABA, increased glutamate) during sleep deprivation.
Which sleep stage is dominated by delta waves?
N3 (deep sleep)
Also known as slow-wave sleep (SWS). Associated with restorative functions and memory consolidations. N3 is most associated with parasomnias (night terrors, sleep walking, bed wetting). Can give low-dose benzodiazepines such as clonazepam for pharmacotherapy for parasomnias.
Non-REM sleep increases neuronal synchrony, thus seizures can absolutely happen during sleep, especially during N3 where wave activity is high in amplitude and lower in frequency.
This seizure presents with rhythmic jerking and postictal confusion.
Tonic-clonic seizure
Name one genetic mutation linked to epilepsy
SCN1A mutation (Dravet syndrome), KCNQ2/3 mutation, GABRG2, and others.
GABRG2 is a gene that codes for the gamma-2 subunit of the GABA receptor. Mutations in this gene can cause loss or dysfunction of the subunit, meaning the receptor is also less functional, leading to neuronal hyperexcitability.
What is the first-line emergency drug for status epilepticus?
Benzodiazepine e.g. IV lorazepam.
If it persists, typically administer fosphenytoin. If refractory status epilepticus (RSE), administer pentobarbital.
Rationale: benzodiazepines to stop seizure, fosphenytoin to maintain control, barbiturates for refractory cases.
What imaging modality is the most useful to identify structural causes of epilepsy?
MRI.
EEG is used to detect brain activity, but MRI can detect structural causes of seizures i.e. cortical stroke, vascular malformations, tumors, inflammatory, sclerosis, etc.
Useful for determining potentially curative therapies (targeted pharmacotherapy, neurosurgery).
What are sleep spindles and K-complexes seen in?
N2 sleep.
We spend about 45-55% at the N2 stage. N2 wave activities are theorized to:
Protect sleep from external disturbances and consolidate memory
These seizures have preserved consciousness with motor or sensory symptoms
Simple focal seizure / Focal aware seizure
or
Myoclonic Seizures
What condition features cortical tubers and is linked to epilepsy?
Tuberous Sclerosis.
TS is defined by hamartomas. Imagine cortical tubers a.k.a. hamartomas in the cortex. Disorganized tissue can lead to seizures.
What anti-epileptic drug is contraindicated in pregnancy due to teratogenicity?
Valproic acid
Highly teratogenic especially during first trimester, interferes with neural tube closure.
Lamotrigine/Levetiracetam are other broad spectrum antiepileptic drugs (AEDs).
broad-spectrum = both focal and generalized, narrow-spectrum = only focal, can worsen generalized
What is the most radical type of treatment for epilepsy?
Surgery for epilepsy (implantable nerve stimulator such as DBS devices, temporal lobectomy, focal cortical resection, corpus callosotomy, hemispherectomy).
Least to most invasive management: lifestyle, pharmacotherapy, neuromodulation, surgery.
REM sleep EEG patterns most closely resemble those of which state of consciousness?
Awake state (eyes open). Defined by beta waves.
Due to cortical activation by pontine cholinergic pathways such as the ascending reticular activating system in the brainstem (a.k.a. paradoxical sleep).
What differentiates absence seizures from complex focal seizures?
Brief duration, no postictal confusion, generalized EEG pattern
What are channelopathies, and why are they important in epilepsy?
Ion channel mutations altering neuronal excitability.
Altered Na+, K+, and/or Ca2+ channels can change the threshold and refractory period of neuronal membranes.
What dietary therapy can help with refractory epilepsy?
Ketogenic diet (apparently evidenced based and seems to work in a decent amount of cases! Though not first-line therapy. Very strict monitoring of diet choices and proportions).
Enhances GABAergic tone, glutamatergic excitation.
What is the legal driving restriction time period (+/- 2 months) post-seizure in Florida?
6 months seizure free if under regular medical supervision and apply for consideration, 2 years if not.