Fisch EEG Primer Chapter 20 Flashcards
Localized Slow Waves
What is the cause of local slow waves?
circumscribed abnormality located superficially or deeply within a hemisphere (e.g. cerebral white matter). Usually has an acute or progressive course (ischemi or seizures, tumors, hemorrhage, abscess, migraine, hypertensive encephalopathy)
Focal slow waves consists of waves less than…
8Hz - usually only focally located but can rarely be over entire hemisphere
focal irregular delta activity is commonly referred to as…
focal polymorphic delta activity
what type of reactivity is typically seen with focal irregular delta activity?
little attenuation with eye opening and may NOT be facilitated by hyperventilation whereas surrounding theta activity MAY respond to these maneuvers - these areas are most conspicuous during transition between wakefulness and light sleep.
Structural lesions producing focal polymorphic delta activity typically demostrate
continous activity of variable waveform, amplitude, duration, and morphology that are persistent during sleep and eye opening maneuvers
What are some transient cerebral disorders that can cause focal slow waves?
TIA, migraine, hypertensive and metabolic encephalopathies, post ictal, head injuries
What is the time period of maximal slow wave activity following structural damage?
Immediately following damage
What is the spatial relationship between focal slow waves and underlying cerebral lesions?
superficial lesions are fairly precise indicators however can appear more lateral or anterior.
What are some other features of EEG in those with focal slow waves that will help in making a clinical diagnosis?
- widespread asynchronous slow waves -usually from acute vascular or metabolic changes
- bilaterally synchronous slow waves - usually deep midline structures (e.g. FIRDA - potential sign of pending herniaiton)
- focal spike and sharp waves - possible ongoing epileptiform activity
- asymmetry and reduced reactivity of the alpha rythym - posterior lesions
What are some degenerative disorder that can produced focal slowing?
Alzheimer’s disease, Jakob-creutzfeld, normal pressure hydrocephalus, porencephaly, tuberous sclerosis, holoprosencephaly, bilateral retrobulbar neuritis in children
What are some metabolic disorders that can produced focal slowing?
hypoglycemia, hypoxia, non-ketotic hyperglycemia, porphyria, vitamin B12 deficiency, Wilson’s disease
What are some cerebrovascular disorders that can produce focal slowing?
ischemia, embolism, hemorrhage, migraine especially if associated with unilateral neurological deficit, tia, chronic subdural, sah
What are some traumatic/ injuries that can produced focal slowing?
brain surgery, progressive traumatic encephalopathy, hemispherectomy
What is the significance of brain tumors and focal slowing?
AMONG THE MOST IMPORTANT CAUSES OF FOCAL SLOWING`
