Basic principle in neuroanatomy

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First found May 22, 2018

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แพทย์หญิง กาญจนา พิทกั ษ์ วฒ
ั นานนท์
อายุรแพทย์ผ้ เู ชี่ยวชาญระบบประสาท
แพทย์ประจาศูนย์สมอง โรงพยาบาลสมิติเวชศรี ราชา
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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
Recording in
response to a
variety of sensory
stimuli
SSEP
VEP
AERP
BERP
Measured in terms
of latency and
amplitude
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
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Optic neuritis ( highly sensitive )
Anterior ischemic optic neuropathy
Sarcoidosis
Leber’s hereditary optic neuropathy
Papilledema
Chiasmal tumors ( eg.,pituitary adenoma )
Psychogenic visual loss ??
Clinical applications
• brain death
• coma from ??
• cortical dysfunction
• brainstem dysfunction
• acoustic neuromas ??
• early detection subclinical MS
From peripheral nerve to sensory cortex
Motor nerve & sensory nerve
amplitude
latency
conduction velocity
Afferently CN V ( sensory )
Efferently CN VII ( motor )
Insertion activity
Spontaneous activity
Muscle contraction activity
Neuromuscular transmission
Peripheral neuropathy
Plexopathy
Nerve root
Spinal cord lesion
For diagnosis and treatment
Normal / LEMS
MG
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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.
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T1 : spin-lattice relaxation
T2 : spin-spin relaxation
TR : repetition time
TE : echo time
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Short TR
Short TE
Best displays anatomy
Bright  Dark
 Fat , flowing blood ,
White matter , Gray matter ,
CSF ,
Bone , Air , Calcium ,
Hemosiderin , Flow void , Infarct
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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
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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.
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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 )
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
Clinical applications
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Epilepsy : SPECT increase in ictal period
Neoplasm : high rate of metabolism
Dementia : hypometabolism
Brain death
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