neurophysiological investigations

34
Mohamed Wael Samir MD Professor of neurosurgery Ain Shams University Neuro-investigations Part II: Neurophysiolgy

Upload: mohamed-hamza

Post on 02-Nov-2014

903 views

Category:

Health & Medicine


1 download

DESCRIPTION

 

TRANSCRIPT

  • 1. Neuro-investigations

2. EEGEvoked PotentialsENS & EMG 3. EEG lecture ILOs Enumerate indications of EEG Describe different types of EEG Enumerate the different MRI sequences andtheir main usages Describe EEG procedure Interpret normal EEG Interpret common abnormalities in EEG Define Polysomnography &Magneto-enchephalography 4. Indication of EEG Some diseases as herpes simplex encephalitis ?? Sleep disorders Altered level of consciousness & brain death Epilepsy: Identify a focal or lateralized epileptogenic source, provide a guide to prognosis follow the course of the disorder 5. Facts It must be stressed that the diagnosisof epilepsy is a clinical one. EEG isnormal in 10-40% of patients withepilepsy.EEG is abnormal in 24% of thepopulation who do not have epilepsy. 6. Facts EDs are recorded on the first EEG in 30%to 50% of patients with epilepsy and in 60%to 90% by the third EEG. Additional EEGsdo not increase the yield further. Thus, 10%to 40% of patients with epilepsy will nothave interictal discharges, even withrepeated EEGs. Sleepdeprivation, hyperventilation, and photicstimulation increase the yield of EDs in somepatients. 7. Types of EEG 8. The International 10-20 system ofelectrode placementFPZFZP3F3 C3 TP3F7 O1 CZFP1 T5T3 T1 PZOZ 9. EEG Interpretation Duration of the wave (Frequency of the waves): 1) Delta range of frequency: 0.5-3.5 Hz 2) Theta range of frequency: 4-7.5 Hz 3) Alpha range of frequency: 8-12.5 Hz 4) Beta range of frequency: 13 Hz or more Amplitude of the wave: Shape of the wave:Short duration = High frequencyLow amplitude Long duration = Low frequency High amplitude 10. Normal EEG 1) Alpha rhythm: normal rhythm in adult duringwakefulness especially seen posteriorly with eyesclosed2) Beta rhythm: normal rhythm in adult seen infrontal region and not affected by eye opening3) Theta and delta rhythms: Seen in children andyoung adults especially in frontal and temporalregions. 11. Abnormal EEG A) Theta or delta slowing: either focal or generalizedB) Persistent frequency asymmetries of greater than 1Hz between corresponding scalp regionsC) Epileptiform discharge: 1) Sharp waves: duration 70-200 ms 2) Spikes discharge: duration 20-70 ms 12. E.g. 13. Magnetoenchephalography Recording of the magnetic field of electrocerebralactivity 14. Evoked Potentials lecture ILOs Enumerate indications of EEG Describe different types of EEG Enumerate the different MRI sequences andtheir main usages Describe EEG procedure Interpret normal EEG Interpret common abnormalities in EEG Define Polysomnography &Magneto-enchephalography 15. Visual Evoked Potentials 16. Brainstem auditory evoked potentials (BSAEPs) cochlea: acoustic nerve: cochlear nerve: superior olivary nucleus in lower pons: lateral lemniscus in mid or upper pons: upper pons or inferior colliculi 17. Somatosensory evoked potential (SEP)cortexUpper brain stem lower brain stemthe cervical cord 18. Motor evoked potential (MEP) 19. EMG lecture ILOs Enumerate indications of EEG Describe different types of EEG Enumerate the different MRI sequences andtheir main usages Describe EEG procedure Interpret normal EEG Interpret common abnormalities in EEG Define Polysomnography &Magneto-enchephalography 20. Normal Electromyography At rest: On contraction: Recruitment and Interference Patterns:A B 21. Abnormal Resting EMG 22. Abnormal MUAPNM 23. Abnormal Recruitment & Interferences Patterns 24. EMG sequence of events in nerve injury Immediately after nerve injury:collateral sprouting Incomplete injury: Late recruitment picket-fence pattern Complete injury: Within the first few weeks (Up to 5 weeks): Sharp positive spikes. Spontaneous Fibrillation . If nerve regeneration started:MUAP: short, small & polyphasic MUAP long, large & polyphasic If no nerve regeneration: nerve regeneration 25. ENG lecture ILOs Enumerate indications of EEG Describe different types of EEG Enumerate the different MRI sequences andtheir main usages Describe EEG procedure Interpret normal EEG Interpret common abnormalities in EEG Define Polysomnography &Magneto-enchephalography 26. Electro Neurography ENG orNerve Conduction Study NCS DemyelinationAxona Degeneration1) The distal latency 2) Response amplitude: 27. F-waveSupramaximal stimulus at a short duration 28. H reflexessubmaximal stimulus at a long duration