Neurological Investigations

1
Neurological Investigations

• Refer to Chapter 11 of
• Clinical Neurology Textbook

2
Neurological Investigations

• Lumbar Puncture
• Indications for CSF Study
• Diagnosis of Infective or inflammatory disorders
• Assessment of the response to therapy
• Administration of medications or contrast
• Reduce CSF pressure (rarely a indication)
• Contraindications
• Suspected intracranial mass
• Local infection
• Coagulopathy
• Suspected spinal cord mass

3
Neurological Investigations

• Lumbar Puncture
• Analysis
• Appearance
• Normal Clear Colorless
• Cloudy or Turbid High WBC gt 200/ul
• Pink Hemoglobin present
• Yellow Bilirubin
• Black Melanin (rare)
• Pressure
• Normal 180-120 mm H2O

4
Neurological Investigations

• Lumbar Puncture
• Analysis
• Microscopic Evaluation Includes
• Cell Count Differential
• lt or to 5 leukocytes/ul
• No neutrophils or RBCs
• Sterile
• Grams Stain for bacteria
• Acid-Fast Stain mycobacteria TB, Leprosy
• India Ink Fungi - cryptococcus

5
Neurological Investigations

• Lumbar Puncture
• Analysis
• Bloody CSF
• Traumatic Puncture
• Supernatant is colorless
• Usually clears w/I 24 hrs
• SAH
• Supernatant is yellow (bilirubin) d/t breakdown
  of hemoglobin to bilirubin
• Remains for a minimum of 6 days

6
Neurological Investigations

• Electromyography (EMG)
• Activity at Rest
• No spontaneous activity
• Fibrillation Potentials
• Duration 5 msec Frequency 20x/sec
• Positive Sharp Waves
• Duration 10 msec Frequency 100x/sec
• Fasciculation Potentials
• Spontaneous activation of all fibers in motor
  units

7
Neurological Investigations

• Electromyography (EMG)
• Activity During Muscle Contraction
• Normal
• Motor unit consits of a LMN all the fibers it
  innervates
• Motor Unit Potentials defined by duration,
  amplitudes, configuration, firing rates
• Limited by muscle being studied of units
  activated

8
Neurological Investigations

• Electromyography (EMG)
• Activity During Muscle Contraction
• Myopathies
• of fibers is ?
• Mean duration amplitude ?
• ? of untis needed for voluntary activity
• Neuropathic Disorders
• of units ? not fibers
• Mean duration amplitude ?
• ? rates of firing
• Clinical Pearl

9
Neurological Investigations

• Nerve Conduction Studies
• Basics
• Performed in conjunction w/ EMG studies
• Used to determine the functional integrity of the
  peripheral nerves
• Nerve stimulated _at_ 2 or more points along its
  course and the response is recorded in one of the
  innervated muscles

10
Neurological Investigations

• Nerve Conduction Studies
• Motor Conduction Studies
• Needle Placement
• Active Electrode
• Reference Electrode
• CMAP or M-Wave
• Conduction Velocity
• Arms 50-70 m/sec
• Legs 40-60 m/sec

11
Neurological Investigations

• Nerve Conduction Studies
• Sensory Conduction Studies
• Orthodromic Stimulation
• Antidromic stimulation

12
Neurological Investigations

• Nerve Conduction Studies
• Results
• Focal Conduction Block
• Motor CMAP elicited by stimulation of the nerve
  above the site of the lesion ? amplitude vs.
  distal stimulation
• Sensory action potentials are ? when the lesion
  is located between the stimulation recording
  sites

13
Neurological Investigations

• Nerve Conduction Studies
• Results
• Conduction Slowing both motor conduction
  velocities are slowed around the lesion
• Motor CMAP is ? as the distance between the stim
  recording electrode increase
• Sensory Action potentials markedly attenuated
• Axon-loss Lesions
• Attenuated muscle response
• Absent sensory action potentials
• EMG signs of denervation
• Motor sensory conduction normal

14
Neurological Investigations

• Nerve Conduction Studies
• Indications for Study
• Location of the sensory lesion
• Neuromuscular dysfunction relationship to
  peripheral nerve disease
• Detect Subclinical Involvement
• Focal lesion w/ mononeuropathy
• Polyneuropathy vs Mononeuropathy Multiplex
• Response to treatment
• Pathological Change in peripheral nerve disorders

15
Neurological Investigations

• Repetitive Nerve Stimulation
• Basics
• Amount of Ach determines size of endplate
  potential
• Ach is usually released in excess
• ? Ach will alter the of fibers activated
  altered size of CMAP
• Conclusion the size of the electrical response
  evoked by either 2 or more supra-maximal stimuli
  or 1 stimulus over 30 sec reflects the efficacy
  of the neuromuscular transmission

16
Neurological Investigations

• Repetitive Nerve Stimulation
• Normal Response no change
• Myasthenia Gravis
• Progressive ? in response
• Lambert-Eaton Syndrome
• Initial response ?
• Over time ? response