EEG in Metabolic Diseases Dr.Roopchand.PS Senior Resident Academic Department of Neurology TDMC, Alappuzha.
EEG in Metabolic Diseases
Dr.Roopchand.PSSenior Resident AcademicDepartment of Neurology
TDMC, Alappuzha.
Introduction:
• Diffuse brain dysfunction due to impaired nutrition to glia and neurons.
• EEG changes have progressive alterations.
– Parallels the severity of encephalopathy.
• Help in prognostication.
• Helps in differentiating between seizure and psychogenic cause of altered sensorium.
Sequence of EEG changes:
• Early stage: patient alert – α slowing mixed with regular theta waves. Bisynchronous generalized frontal theta-delta activity attenuated by eye opening.
• Paradoxical arousal response: frontal slowing may become apparent on eye opening.
• Stage 2: generalized theta activity with less reactivity to eye opening.
• Stage 3: variable delta slowing with increase in voltage.
• Stage 4: severe encephalopathy – low voltage continuous or intermittent delta activity or burst suppression pattern.
Hepatic Encephaloopathy:
• Pathology due to increased ammonia.
– Enhances GABA transmission.
• Octopamine, manganese.
• Degree of slowing parallels the rise in ammonia.EEG changes are sensitive and accurate indicator of CNS involvement.
• Triphasic waves are seen.
– Initial low voltage negative wave followed by a prominent positive sharp wave and broad negative wave.
– 2-4Hz, anterior location, slowed back ground.
– Not pathognomonic
EEG changes according to level of consiousness:
Stage Consciousness EEG
1 Alert Normal
2 Drowsy Slow alpha, poorly developed k complexes, sleep spindles
3 Stupor Theta activity with occasional FIRDA, absence of sleep pattern.
4 Coma Triphasic waves
5 Deep coma Delta waves, triphasicdisappear.
6 Deep coma Flat EEG
Reye’s Syndrome:
• EEG may correlate with prognosis
• Grade 1&2: Slow background of theta-delta activity – patients often survives.
• Grade 3: intermediate changes – 50% survival
• Grade 4 &5: low voltage non reactive delta activity or burst suppression – either dies or survives with major sequel.
Wilson’s Disease:
• EEG is normal in majority.
• May show pronounced slowing.
• Decreased sleep spindles and occasional spike discharges.
• Changes do not correlate
Renal Diseases:
Uremic encephalopathy:
• Changes depends more on acuteness.
• Seizure can be focal or generalized.
– Due to water and electrolyte imbalance.
• EEG changes parallels level on consciousness.
• Early stage: slowing of alpha mixed with diffuse or bitemporal theta activity.
• Alternating pattern: normal frontal delta.
• Severe encephalopathy: diffuse slowing
• Paradoxical arousal response may be seen.
• IPS : photomyoclonic or photoparoxysmalresponse.
• Triphasic waves also may be sen.
Dialysis Disequilibrium syndrome:
• Occurs during or immediately after dialysis.
• Head ache, nausea, fatigue, confusion, fasciculation's, convulsions, coma
• Sudden transient osmotic changes and electrolyte changes.
• EEG reflects the uremia prior to dialysis.
• Bursts of delta, rhythmic delta activity, rhythmic theta activity with normal background activity.
Dialysis Dementia:
• Occur to patients on c/c dialysis.
• Progressive dementia after 3-4 yrs.
• EEG pattern may appear months before onset of dementia.
• 2-4hz high voltage irregular frontally dominant delta waves– Vertex waves, sharp waves, triphasic waves, spikes
with normal background.
• Slowing of background with clinical disease.
Action myoclonus renal failure syndrome:
• AR disorder manifest in late adolescence.
• Hand tremor, action myoclonus cerebellar signs, generalized seizure, proteinuria and progressive seizures.
• Slowing of background with epileptiform discharges.
• Hv – paroxysmal discharge
• IPS – photoparoxysmal response.
• Hyponatremia: rhythmic delta activity can occur.
– EEG changes can remain for long durations even after correction of hyponatremia.
• Hypoglycemia: slowing of background and epileptiform discharges.
– Changes disappear once hypoglycemia corrected.
– Summation effect: permanent EEG changes in prolonged hypoglycemia.
• Hyperglycemia: if > 400mg% - slowing mixed with fast activity.
• In DKA slowing parallels with depth of coma
• PLEDS may be seen in Epilepsia partialiscontinua.
• Thyrotoxicosis: augmentation of alpha activity with central beta activity.
• Thyroid storm: high amplitude delta spike and sharp waves, burst suppression and triphasicwaves.
• Hashimoto encephalopathy: diffuse slowing, medial temporal lobe focal epileptiform discharges, triphasic waves and periodic activity.
• Myxedema: poor maturation of EEG.
• Adrenal insufficiency: background slowing, poor response to eye closure reduced beta and increased sensitivity to HV.
• Alpha slowing may be seen at the end of pregnancy and 1-3 days prior to menstruation.
• Hypocalcemia: Seizure occur at serum level >5mg%– EEG changes do not correlate with calcium levels.
– Slowing with generalized bursts of spikes.
• Hypercalcemia: background slowing with intermittent rhythmic delta activity.– Prominent photic response > 13mg%
– Focal epileptiform discharges and triphasic waves >16mg%
• Carbon dioxide narcosis: diffuse theta delta activity with occasional triphasic wave.