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Chapter 13: Ancillary Neurodiagnostic Procedures—Lumbar Puncture and Neuroimaging

INTRODUCTION

We have instruments of precision in increasing numbers with which we and our hospital assistants at untold expense make tests and take observations, the vast majority of which are but supplementary to, and as nothing compared with, the careful study of the patient by a keen observer using his eyes and ears and fingers and a few simple aids.

—Harvey Cushing (1869–1939)

I. ARRAY OF NEURODIAGNOSTIC PROCEDURES

After completing the history and neurologic examination (NE) and proposing a tentative diagnosis, the examiner (Ex) has to decide whether further studies are required. Table 13-1 reviews the array of standard diagnostic tests. The goal is to choose the one or two safest, least invasive, and most economical procedures that will best confirm or refute the tentative diagnosis. Do not order every conceivable test to cover every diagnostic possibility. Go for the jugular. If you fail initially to secure the diagnosis, select successive tests in a logical order. In this section we will discuss the clinical use of lumbar puncture (LP) and neuroimaging studies.

TABLE 13-1Ancillary Neurodiagnostic Procedures
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TABLE 13-1 Ancillary Neurodiagnostic Procedures

  1. Neuroradiologic imaging

    1. Plain films

    2. CT (enhanced and unenhanced)

    3. MRI (enhanced and unenhanced)

    4. Angiography:MRA, direct injection, CTA, Doppler sonography

    5. Cranial ultrasonography

    6. Radionuclide scanning: PET, SPECT

  2. Electroneurodiagnosis

    1. Electroencephalography (EEG)

    2. Electromyography (EMG)

    3. Nerve conduction velocity (NCV)

    4. Evoked responses: visual, auditory, and somatosensory

    5. Audiogram

  3. Punctures

    1. Subarachnoid (LP or cisternal) for CSF

    2. Subdural for blood, pus, or fluid

    3. Ventricular for blood or CSF

    4. Stereotaxic for lesion biopsy

  4. Blood biochemistry

    1. Complete metabolic profile

    2. Toxicology screen

    3. Quantitative amino acids and organic acids

    4. Serum enzymes

    5. Long-chain fatty acids, cholesterol, cholestanol

    6. Serum ceruloplasmin

    7. B1, B12 and folic acid

    8. Lysosomal enzymes

    9. Collagen vascular screen

    10. Disease-specific tests for inborn errors of metabolism

    11. Hypercoagulable screen

    12. Protein fractionation

  5. Neuro-ophthalmology

    1. Visual acuity

    2. Visual fields, central and peripheral

    3. Ophthalmoscopy direct and indirect, slit-lamp inspection of media and fundus

    4. Visual evoked response (VER)

    5. Electroretinogram (ERG)

    6. Electronystagmography

    7. Optical coherence tomography (OCT)

  6. Urinalysis

    1. Routine including specific gravity

    2. Screen for inborn errors of metabolism

    3. Toxicology screen

    4. Catecholamines

  7. Neuropsychological tests

    1. Developmental

    2. IQ

    3. Achievement

    4. Neuropsychological battery

    5. Personality profile

  8. Biopsy

    1. Muscle

    2. Nerve

    3. Skin

    4. Brain

  9. Microbiologic tests

    1. Serologic

    2. Culture of microorganisms

    3. Immunologic screen, T and B cells, blood titers, γ-globulin

    4. Polymerase chain reaction

  10. Genetic tests

    1. Karyotype

    2. Genotype

ABBREVIATIONS: CSF = cerebrospinal fluid; CT = computed tomography; CTA = Cranial computed tomography angiography; LP = lumbar puncture; MRA = magnetic resonance angiography; MRI = magnetic resonance imaging; PET = positron emission tomography; SPECT = single-photon emission computed tomography.

II. THE CEREBROSPINAL FLUID EXAMINATION

A. Location, origin, and circulation of the cerebrospinal fluid

  1. Examination of the cerebrospinal fluid (CSF) dates to Heinrich Iraneous Quincke who introduced spinal puncture in 1891 for the treatment of hydrocephalus.

  2. Location of the CSF: The CSF occupies the ventricles and subarachnoid spaces. The total volume of ...

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