Epilepsy:
Epilepsy is an Abnormal involuntary excessive electrical activity of the neuronal cell bodies in grey matter of cerebral cortex.
Involuntary: means can’t be controlled by force or will.
Grey matter disease: means other than cerebral grey matter, no other area can explain epilepsy. Eg epilepsy can’t be manifestation of white matter or basal ganglia or cerebellum or brain stem or spinal cord.
S/S depends on the area involved. Motor ( frontal), sensory( parietal) visual ( occopital),gustatory/olfactory/auditory( temporal) psychiatric , emotional or autonomic ( limbic) symptoms or signs. So epilepsy is not just motor over activity.
If starting from one area of cortex, it will give s/s related to that area ( Focal epilepsy/ epilepsy with Aura). If this activity spreads to adjacent area( marching along ) them it’s called focal with Jacksonian pattern epilepsy, if focal epilepsy spread to both the cortex via reticular formation leading to bilateral s/s & loss of consciousness ( focal epilepsy with secondary generalisation).
So D/D of the focal fits is very broad. Repeated episodic s/s followed by post ictal fatigue is an important clue for seizures. Epilepsy usually lasts for a few minutes or so. E.g, episodic psychotic s/s lasting for a few mins followed with post ictal phase may be temporal lobe epilepsy rather than schizophrenia. Repeated episodic autonomic s/s followed by post ictal phase may be Limbic epilepsy rather than photochromocytoma Etc etc.
If it doesn’t start from any particular area, rather involves both the cortex right from the start ( no aura/no focal symptoms), its called Generalised epilepsy. Loss of consciousness is an essential criteria to diagnosis epilepsy. If there is no loss of consciousness, it can’t be generalised epilepsy.
Generalised epilepsy of frontal ( motor type )can be
Tonic: sustained spasm of muscles
Clonic: fine rhythmic jerking which is symmetrical & fine
Tonic-Clonic: spasm followed by clonic phase
Myoclonic: gross asymmetrical limb jerking which is very similar to gross jerks which we get while we are entering into sleep.
Absence: repeated very brief ( for seconds ) episodes of starring look. Happens many times/ day. As we all do in lectures( just kidding).
True generalised epilepsy vs. pseudo epilepsy;
Hip thursting, gross shaking of limbs,asymmetrical shaking of limbs, shaking which can be controlled with force, no loss of consciousness, absence of self harm/incontinence/tongue bite or absence of post ictal phase all favour pseudo epilepsy.
Status epilepticus; continues generalised epilepsy for 15 mins or more. Or repeated episodes of generalised epilepsy without recovery from the previous post ictal phase. It is an emergency & needs ICU admission for airway protection & treatment.
CAUSES:
Any irritation of grey matter can cause epilepsy.
Pressure on cortex ( mass lesions, raised ICP,gliosis etc)
Neuronal swelling ( encephalitis,cerebral oedema etc etc)
Neuronal shrinkage ( hyperosmolar states, high sodium)
Metabolic derangement ( hypoxia, ischemia, hypoglycemia,hypocalcemia, hypomagnessemia, hyponatremia , alkalosis, acidosis etc etc)
Genetic /familial predisposition etc are various causes.
Workup:
Best is the witness or recorded fits. Video record is the best evidence. Any one who has witnessed the fits, his history is very imp.& the most imp point is to differentiate focal from generalised.
Focal epilepsy usually has a focal cause like Mass lesion/scar/bleed/ infarct etc, so neuroimaging like MRI is essential to exclude the focal cause.
Generalised epilepsy is usually either genetic or systemic cause or diffuse cerebral cause. So needs family history, metabolic profile ( see the causes) before we do brain imaging. So brain imaging may not be needed if there is no cerebral cause suspected &metabolic profile or family history gives us the clue.
EEG: during attack is useful. In b/w attacks it can pick 50% of subclinical activity focus while remaining cases EEG is negative, so negative EEG can’t exclude epilepsy. Main role is classifying epilepsy & to some extent diagnostic. Not essential for every one.
Special tests according to the cause suspected: CSF analysis if meningitis or encephalitis suspected.