Lab Interpretation & Neurological examination

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1 Lab Interpretation & Neurological examination 黃英儒 Ying-Zu Huang, MD, PhD Medical School, Chang Gung University Neuroscience Research center & Dept of Neurology, Chang Gung Memorial Hospital Taiwan

2 Nerve conduction velocity (NCV) Nerve conduction studies are commonly performed in the evaluation of suspected neuromuscular diseases and provide an objective measure of pathophysiologic changes. Routine conduction studies evaluate only large myelinated nerve function It includes: Motor NCV, sensory NCV, F-wave, H-reflex

3 Electrode placement for NCV Antidromic sensory S G1 G2 G0 G2 G1 Orthodromic sensory S1 S2 G1 G2 S Motor G0

4 Motor conduction velocity CMAP = compound motor action potential Supramaximal intensity (20-30% above Max.) Two or more stimulation site along the nerve Latency= nerve conduction time + neuromuscular transmission time MNCV= distance (proximal and distal stimulating sites) proximal latency - distal latency

5 Sensory NCV SNAP = sensory nerve action potential More sensitive than motor NCV for detecting mild peripheral nerve dysfunction The amplitude is much smaller than CMAP Antidromic vs. Orthodromic Velocity same Amplitude > Wave form biphasic triphasic

6 Interpretation of NCV Axonopathy Prolongation of latency ++++ Slowing of NCV ++++ Decrease of amplitude ++++~++ Conduction block _+++ Temporal dispersion ++++ Demyelinating

7 F-wave vs. H-refelx F-wave Motor in Motor out H-reflex Sensory in Motor out Sensory nerve Motor nerve Motor nerve

8 Spinal reciprocal inhibition Stimuli H-reflexes Median n. Conditioning Stimulation (Radial n.) Test Stimulation (Median n.) Control Delay 0 ms Radial n. 100 % Delay -1 ms Delay 30 ms

Phases of reciprocal inhibition Size of H-reflex as %

100 300 500 750 Interstimulus Intervals (ms) Phase 3

9 Phases of reciprocal inhibition Size of H-reflex as % control 120% 100% 80% 60% 40% 20% 0% Phase 1 (~0 ms) Disynaptic Ia inhibition Phase 2 (10-20 ms) Premotorneuronal mechanism Interstimulus Intervals (ms) Phase 3 ( ms) (?) polysynaptic long latency stretch reflex pathway

10 Blink reflex

firing pattern Complex repetitive discharge: Originating from multiple muscle fibers

11 EMG: Insertional/spontaneous activity How to differentiate End-plate spike: Irregular firing pattern and representing normal finding Myotonic discharge: Waxing and waning firing pattern Complex repetitive discharge: Originating from multiple muscle fibers time-locked together Fasciculation potential: Irregular firing pattern and is generated from motor axon

12 Other points for EMG How to differentiate neuropathy and myopathy? Jitters in the single fiber EMG How to differentiate MG and Lambert-Eaton syndrome in the repetitive stimulation test?

13 Surface EMG Lower frequency spectrum Record superficial muscles Easy to reposition However, more cross-talk concerns Useful for detecting Tremor, myoclonus (positive & negative) and other movement disorders

14 Evoked Potential An EP is an electrical manifestation of the brain s reception of and response to an external stimulus EPs are very low-amplitude ( µv) responses superimposed on normal EEG activity Unaffected even by general anesthesia or barbiturate levels sufficient to induce coma and flattening of the EEG Generators of EP: Nerve fiber bundles (peripheral & central) Advancing front of the compound action potential Nuclei Axonal action potentials Charge movement during synaptic transmission

15 Major Types of EPs BAEP (Brainstem Auditory Evoked Potential) SEP (Somatosensory Evoked Potential) VEP (Visual Evoked Potential) MEP (Motor Evoked Potential) by TMS

16 BAEP- left ear

17 BAEP vs. Brainstem Wave I : distal CN VIII Wave II : proximal CN VIII or cochlea nucleus Wave III : lower pons (superior olivary complex?) Wave IV: mid to upper pons (lateral lemniscus tract & nuclei?) Wave V : upper pons or inferior colliculus BAEP waveforms are generated ipsilateral to the active ear, except perhaps wave V

18 Import points for BAEP The waveforms and latencies are highly consistent across normal subjects. Resistant to the effects of consciousness, metabolic disturbances and drugs. Wave V is the BAEP component most resistant to the effects of decreasing stimulus intensity Most sensitive screening test for acoustic neuroma. A tool for MS with brainstem involvement abnormalities usually consist of increased III-V interpeak latency.

19 Question (BAEP) Normal peak latency of wave I Prolonged peak latency of wave III Normal interpeak latency of wave III-V Prolonged interpeak latencies of wave I-III & I-V. The wave form of wave III & V is unclear

20 SEP- median nerve

21 Pathway of SEP Sensory nerve low threshold myelinated nerve fibers dorsal root ggl. Ipsilateral dorsal columns Gracile and cuneate nulcei cross Contralateral medial lemniscus Thalamus (VPL) Sensory cortex

22 SEPs to Arm Stimulation P25 N20 N20 Thalamocortical radiation P14: P14: Caudal Caudal medial medial lemniscus P14 N13: N13: Dorsal Dorsal horn horn neurons N11: N11: Posterior column column EP/N9: EP/N9: Afferent volley volley in in plexus plexus

23 SEPs to Leg Stimulation

24 Question of SEP The finding of SSEP does NOT suggest which of the following disease? 選項 : (A) Encephalitis with myoclonus (B) Progressive myoclonic epilepsy (C) Creuzfeldt-Jakob disease (D) Corticobasal ganglionic degeneration (E) Propriospinal myoclonus Kimura. Electrodiagnosis in disease of nerve and muscle

25 VEP VEPs to patterned light VEPs to checkerboard patterns VEPs to sine wave gratings Others: bar gratings, small light spots, random dots VEPs to diffuse light (flash)

26 Flash vs. pattern stimulation Flash Pattern

27 VEPs to Checkerboard Patterns

28 Normal VEP Waveform P100: Generated in striate and prestriate occipital cortex Prolonged P100: evidence of demyelinating injury of the visual pathway

29 Question (VEP)

30 Transcranial magnetic stimulation (TMS)

31 Common Sites to Stimulate Transcranial Latency= central+root+peripheral Cervical root Latency= peripheral Lumbar root Latency= peripheral Sciatic nerve Latency= peripheral

32 Transcranial magnetic stimulation (TMS) Magnetic nerve stimulation? A noninvasive method for the stimulation of neuromuscular tissue The magnetic field functions as the vehicle that causes ion flow in the body and does not itself stimulate the nerve Transcranial electrical stimulation (TES) may induce more stable MEPs, but painful.

33 Central motor conduction time (CMCT)- TMS only Latency of transcranial stimulation Latency of root stimulation CMCT =central + motor neuron to root Motor neuron

34 Central motor conduction time (CMCT)- TMS + F wave Latency of transcranial stimulation (Latency of F wave + latency of M response 1ms)/2 CMCT ~ central Motor neuron

Cervical spondylosis C. Parkinson disease D.

35 Question of MEP The finding of this MEP study is MOST COMPATIBLE with which of the following diseases? A. Cerebral palsy B. Cervical spondylosis C. Parkinson disease D. Amyotrophic lateral sclerosis E. Huntington disease Neurology in Clinical Practice, 6th Edition p. 390

36 Important points for MEPs MEPs are frequently abnormal in patients with myelopathies caused by cervical spondylosis. In motor neuron disease, pyramidal tract conduction delays are demonstrable in patients without upper motor neuron signs. MEP latencies and amplitudes are usually normal in movement disorders. Cerebral palsy may demonstrate enhanced MEPs in some muscle groups.

37 Other Lab investigations Antibodies & proteins for neurological disorders Anti-NMDA receptor antibodies in temporal lobe epilepsy Anti-GM1 gangliodise antibodies in multiple motor neuropathy M protein in osteosclerotic myeloma and POEMS syndrome Anti-AQP4 antibodies in neuromyelitis optica CSF studies (including the pressure) for infection and other diseases. Neuroimages of certain diseases.

38 Neurological Examination Signs vs. Localization is the most important point Eye signs Pupil vs. location and cause Ptosis vs. location and cause Nystagmus vs. location and cause Upbeat nystagmus: Cerebellar vermis or medulla Seesaw nystagmus: Ant. third ventricle Ocular bobbing: Pons Convergence-retraction nystagmus: Rostral midbrain, pretectum, post. Commissure, post. third ventricle

39 Arrangement of spinal tracts S L TC CTLS CTLS

40 Other points for NE NE of certain intoxication mercury intoxication lead intoxication thallium intoxication cadmium intoxication chromium intoxication etc. Pictures of some typical presentation may be shown for the answer Questions may combine NE and Labs

41 Symphony of dopamine & non-invasive brain stimulation 時間 :2015 年 11 月 21 日 ( 全天 ) Training course of non-invasive brain stimulation 2015 年 11 月 22 日 ( 上午 ) Dancing with dopamine and NiBS 地點 : 台南成大會館

Audit and Compliance Department 1

Audit and Compliance Department 1 Introduction to Intraoperative Neuromonitoring An intro to those squiggly lines Kunal Patel MS, CNIM None Disclosures Learning Objectives History of Intraoperative Monitoring What is Intraoperative Monitoring