EEG brain for medical investigation and
management แพทยหญง กาญจนา พทกษวฒนานนท
อายรแพทยผเชยวชาญระบบประสาท แพทยประจำาศนยสมอง โรงพยาบาลสมตเวชศรราชา
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
Electroencephalography : EEG
Scalp EEG
Epidural EEG / Subdural EEG
Electrocorticography
EEG – Photic stimulation
Evoked potential : EPRecording in response to a variety of sensory stimuli
SSEPVEPAERPBERP
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 ??
Brainstem auditory evoked potentials : BAEP
BAEP + AERP
Clinical applications
• brain death• coma from ??• cortical dysfunction• brainstem dysfunction
• acoustic neuromas ??• early detection subclinical MS
Auditory evoked potential : AERP
Somatosensory evoked potentials : SSEP
From peripheral nerve to sensory cortex
Nerve conduction studies : NCS
Motor nerve & sensory nerveamplitudelatencyconduction velocity
Blink reflex
Afferently CN V ( sensory )
Efferently CN VII ( motor )
Electromyography : EMG
Neuromuscular transmissionPeripheral neuropathyPlexopathyNerve rootSpinal cord lesion
Insertion activitySpontaneous activityMuscle contraction activity
Needle electromyographyFor diagnosis and treatment
Repetitive nerve stimulation test : RNS
MG
Normal / LEMS
Single fiber EMG : SFEMG
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
MRI scan
Short TR Short TE Best displays anatomy Bright Dark
Fat , flowing blood , White matter , Gray matter , CSF , Bone , Air , Calcium , Hemosiderin , Flow void , Infarct
T1- 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
T2 weighted images
MRI – Brain tumor
MRI – Brain metastasis
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
)
fMRI ( functional magnetic resonance
imaging )
fMRI
Diffusion tensor imaging : DTI
Tractography
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
1. Epilepsy : SPECT increase in ictal period2. Neoplasm : high rate of metabolism3. Dementia : hypometabolism4. Brain death
Functional neuroimaging
Single photon emission computed tomography : SPECT
Positron emission tomography : PET