Seizures and epilepsy

A seizure refers to a one-time event caused by abnormal, excessive, and synchronous electrical activity in the brain that can result in autonomic, sensory, and motor symptoms. When seizures specifically involve motor activity, like jerking, we call them convulsions. Most seizures last less than 5 minutes, but if the seizure continues for 5 minutes or more, it’s called status epilepticus.

Keep in mind that seizures are a symptom, not a diagnosis, meaning they can occur due to various underlying causes, such as trauma, infections, and metabolic imbalances. However, when seizures arise without a clear cause, they are considered unprovoked. And if someone experiences two or more unprovoked seizures, at least twenty-four hours apart, think epilepsy.

Normally, the brain and its neurons rely on a balance between excitatory and inhibitory neurotransmitters. Think of excitatory neurotransmitters like green traffic lights that speed things up, encouraging the neuron to pass electrical impulses to the next one. On the other hand, inhibitory neurotransmitters act like red traffic lights that slow traffic down, stopping the further propagation of electrical impulses.

Now, whether there’s too much excitation or not enough inhibition, neurons can begin firing impulses simultaneously. This leads to abnormal, excessive, and synchronous electrical activity in the brain, which results in a seizure.

Now, there are various causes of seizures, and you can remember the most important ones using the mnemonic “VITTAMINS”. “V” stands for Vascular conditions, like strokes and intracranial hemorrhage, and “I” covers Infection, including meningitis, encephalitis, and brain abscess. Next, the first “T” refers to head Trauma, while the second “T” refers to Toxins, such as cocaine or amphetamine overdose, but also alcohol withdrawal. “A” is for Autoimmune conditions, such as CNS vasculitis and lupus; and “M” is for Metabolic conditions, including hepatic- and uremic encephalopathy, as well as electrolyte disturbances, such as hyponatremia. The second “I” is for Idiopathic, meaning no identifiable cause, which refers to epilepsy. Finally, “N” is for neoplasm or brain tumors, and “S” covers differential diagnoses like Syncope, pSychogenic seizures, and migraineS.

Now, based on where the abnormal activity starts, seizures are broadly classified into generalized and focal seizures.

Generalized seizures arise from both cerebral hemispheres and almost always cause a sudden impairment of consciousness. This type of seizure can be further subdivided into generalized motor- and non-motor seizures.

Generalized motor seizures, as their name implies, involve muscle activity and include several types. First, tonic seizures are characterized by a significant increase in muscle tone that results in stiffness and rigidity. Next, clonic seizures are associated with repeated, rapid, rhythmic jerking movements, usually of arms and legs. These episodes can last from several seconds to a couple of minutes.

Also, there’s a combination of the two patterns, called tonic-clonic seizures, which combine muscle stiffening with muscle jerking. During tonic-clonic seizures, a person may experience a sudden contraction of their vocal cord muscles, resulting in an involuntary scream or cry. Also, the eye muscles can contract, causing the eyes to roll back, while the contraction of the oropharyngeal muscles can impair swallowing, causing saliva to pool in the oropharynx. On top of that, the jaw muscles can contract and result in tongue biting. In this case, a person might also lose control of their bladder or bowels during the seizure, resulting in urinary and fecal incontinence.

Next, we have atonic seizures, which basically mean seizures with “no muscle tone”. In this type, there's a sudden loss of postural muscle tone lasting 1 to 2 seconds, causing the individual to collapse to the ground. On the flip side, myoclonic seizures involve sudden, brief, rapid muscle twitches that last only a fraction of a second. Finally, there’s a combination of the previous two, called myoclonic-atonic seizure, marked by rapid muscle twitches followed by a brief loss of muscle tone and collapse.

Alright, moving on to generalized non-motor seizures, also known as absence seizures, which are most common in children and adolescents. These seizures cause a brief loss of consciousness, particularly awareness, without any change in the postural muscle tone. It’s like the brain hits the “pause” button for a moment, then quickly presses “play” again. For example, a student might be sitting in a class, listening to a lecture, and suddenly zone out, only to snap back to reality several moments later. Unfortunately, these episodes can occur hundreds of times per day, and parents and teachers often think the child is just stareing off into space or not paying attention.

Furthermore, absence seizures are subdivided into typical- and atypical absence seizures. Typical absence seizures come on quickly, usually last up to 20 seconds, and have a fast recovery. On the other hand, atypical absence seizures are slower in onset, last more than 20 seconds, and take more time to recover from. After atypical absence seizures, individuals often appear confused or dazed.