แพทย์หญิง กาญจนา พิทักษ์วัฒนานนท์ อายุรแพทย์ผู้เชี่ยวชาญระบบประสาท แพทย์ประจำศูนย์สมอง โรงพยาบาลสมิติเวชศรีราชา

 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 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 )

Neuromuscular transmission Peripheral neuropathy Plexopathy Nerve root Spinal cord lesion Insertion activity Spontaneous activity Muscle contraction activity

For diagnosis and treatment

MG Normal / LEMS

 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

 Short TR  Short TE  Best displays anatomy  Bright  Dark  Fat, flowing blood, White matter, Gray matter, CSF, Bone, Air, Calcium, Hemosiderin, Flow void, Infarct

 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

 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 )

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 ) 18 F-deoxy-glucose, a positron-emitting nucleotide

Clinical applications 1. Epilepsy : SPECT increase in ictal period 2. Neoplasm : high rate of metabolism 3. Dementia : hypometabolism 4. Brain death