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EEG brain for medical investigation and management. แพทย์หญิง กาญจนา พิทักษ์วัฒนานนท์ อายุรแพทย์ผู้เชี่ยวชาญระบบประสาท แพทย์ประจำศูนย์สมอง โรงพยาบาลสมิติเวชศรีราชา. Electroencephalography : EEG.
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EEG brain for medical investigation and management แพทย์หญิง กาญจนา พิทักษ์วัฒนานนท์ อายุรแพทย์ผู้เชี่ยวชาญระบบประสาท แพทย์ประจำศูนย์สมอง โรงพยาบาลสมิติเวชศรีราชา
Electroencephalography : EEG • The activity recorded in the EEG originates mainly from the superficial layers of the cerebral cortex. • Current is believed to flow between cortical cell dendrites and cell bodies • As a result of the synchronous activation of axodendritic synapses on many neurons , summed electrical currents flow through the extracellular space , creating the waves recorded as the EEG • Clinical applications • Seizure • Sleep disorder • Encephalopathy
Evoked potential : EP Recording in response to a variety of sensory stimuli SSEP VEP AERP BERP Measured in terms of latency and amplitude
Visual evoked potentials : VERP The most common stimulus involves alternating light and dark checkerboard squares P100 or P1 latency refers to a positive deflection recorded over the occiput , normally occurring around 100 millisecs • Clinical applications • Optic neuritis ( highly sensitive ) • Anterior ischemic optic neuropathy • Sarcoidosis • Leber’s hereditary optic neuropathy • Papilledema • Chiasmal tumors ( eg.,pituitary adenoma ) • Psychogenic visual loss ??
BAEP + AERP • Clinical applications • brain death • coma from ?? • cortical dysfunction • brainstem dysfunction • acoustic neuromas ?? • early detection subclinical MS
Somatosensory evoked potentials : SSEP From peripheral nerve to sensory cortex
Nerve conduction studies : NCS Motor nerve & sensory nerve amplitude latency conduction velocity
Blink reflex Afferently CN V ( sensory ) Efferently CN VII ( motor )
Electromyography : EMG Insertion activity Spontaneous activity Muscle contraction activity Neuromuscular transmission Peripheral neuropathy Plexopathy Nerve root Spinal cord lesion
Needle electromyography For diagnosis and treatment
Repetitive nerve stimulation test : RNS Normal / LEMS MG
MRI scan • MRI involves first alingning the protons within human tissues in a strong magnetic field • The alinment is briefly interrupted via generation of a radiofrequency pulse. • The relaxation characteristics of protons in various tissues are then recorded as they recover magnetization. • T1 : spin-lattice relaxation • T2 : spin-spin relaxation • TR : repetition time • TE : echo time
T1- weighted images • Short TR • Short TE • Best displays anatomy • Bright Dark • Fat , flowing blood , White matter , Gray matter , CSF , Bone , Air , Calcium , Hemosiderin , Flow void , Infarct
T2 weighted images • Long TR • Long TE • Best highlights pathology • Bright Dark • CSF , Edema , Neoplasms , Abcess , Demyelination , Infarct , Gray matter , White matter , Bone , Air , Calcium , Hemosiderin , Flow void , Fat
fMRI ( functional magnetic resonance imaging ) • An image sensitive to local changes in the concentration of deoxyhemoglobin. • MRI can provide maps that show regions of increased neural activity within the brain. • Motor activity ( eg., tapping of fingers ) • Sensory activity ( eg., stimulation part of body surface ) • Cognitive activity ( eg., calculation , reading , recalling ) • Affective activity ( eg., responding mentally to a fearful stimulus )
Functional neuroimaging SPECT ( Single photon emission computed tomography ) • Studies the uptake of gamma-releasing radionucleotides ( eg., hexamethylpropyleneamineoxime : HMPAO ) as a measure of blood flow PET ( Positron emission tomography ) • A functional imaging study that correlates activity to glucose uptake and metabolism by measuring ( most commonly ) 18F-deoxy-glucose , a positron-emitting nucleotide
Functional neuroimaging Clinical applications • Epilepsy : SPECT increase in ictal period • Neoplasm : high rate of metabolism • Dementia : hypometabolism • Brain death