Download Neurologic Investigations

Dr. Hawar Adnan Mykhan
M.B.Ch.B., F.I.B.M.S
INVESTIGATION OF
NEUROLOGICAL DISEASE
1. CLINICAL NEUROPHYSIOLOGY
a) Electroencephalography (EEG)
b) Electromyography, Nerve conduction studies and
c)
2.
3.
a)
b)
c)
repetitive nerve stimulation (EMG, NCS, RNS)
Evoked potentials (EP)
IMAGING
SPECIAL TESTS
Blood tests
CSF analysis
Biopsies
CSF analysis
Indications
 Diagnosis of meningitis, inflammatory disorders like Guillain–
Barré syndrome and multiple sclerosis, subarachnoid
hemorrhage, hepatic encephalopathy, meningeal malignancies,
paraneoplastic disorders, or suspected abnormalities of
intracranial pressure.
 Assessment of the response to therapy in meningitis and other
infective or inflammatory disorders.
 Administration
of
intrathecal
medications
like
chemotherapeutic agents and antibiotics or radiologic contrast
media.
 to reduce cerebrospinal fluid (CSF) pressure.
Contraindications
 Suspected intracranial mass lesion. In this situation, performing a
lumbar puncture can hasten incipient transtentorial herniation.
 Local infection overlying the site of puncture. Under this circumstance,
cervical or cisternal puncture should be performed instead.
 Coagulopathy. Clotting-factor deficiencies and thrombocytopenia
(below 20 000/mm3 or rapidly falling platelet counts) should be
corrected before lumbar puncture is undertaken, to reduce the risk of
hemorrhage.
 Suspected spinal cord mass lesion. Lumbar puncture in this case should
be performed only in association with myelography, which is used to
determine the presence and level of structural spinal pathology.
 With a cooperative patient, lumbar puncture can generally be performed
by one person. An assistant can be helpful in positioning the patient and
handling CSF samples, of course, especially if the patient is
uncooperative or frightened.
 Lumbar puncture is usually performed with the patient in the lateral
decubitus position, lying at the edge of the bed and facing away from
the person performing the procedure.
 The patient's lumbar spine should be maximally flexed to open the
intervertebral spaces.
 Occasionally, it is desirable to perform lumbar puncture with the patient
seated. In this case, the patient is seated on the side of the bed, bent over
a pillow that rests on a bedside table, while the physician reaches over
the bed from the opposite side to perform the procedure.
 The usual practice is to enter the L3-L4 or L4-L5
interspace, since the spinal cord (conus medullaris)
terminates at about the L1-L2 level in adults,thus, the
procedure is performed without danger of puncturing the
cord.
 The L3-L4 interspace is located at the level of the
posterior iliac crests.
 Ideally, blood and CSF glucose levels should be measured
in samples obtained simultaneously after the patient has
fasted for at least 4 hours.
Complications
 UNSUCCESSFUL TAP: marked obesity, degenerative disease of
the spine, previous spinal surgery, recent lumbar puncture, and
dehydration, can make it difficult to perform lumbar puncture.
 ARTERIAL OR VENOUS PUNCTURE: If the needle enters a
blood vessel rather than the spinal subarachnoid space, it should be
withdrawn and a new needle should be used to attempt the tap at a
different level. Patients who have coagulopathy or are receiving
aspirin or anticoagulants should be observed with particular care for
signs of spinal cord compression from spinal subdural or epidural
hematoma.
 POST-LUMBAR-PUNCTURE HEADACHE: A mild headache,
worse in the upright position but relieved by recumbency, is not
uncommon following lumbar puncture and will resolve
spontaneously over a period of hours to days.
Analysis of Results
 CSF is normally clear and colorless.
 It may appear cloudy or turbid with white blood cell counts that




exceed about 200/μL
Color can be imparted to the CSF by hemoglobin (pink), bilirubin
(yellow), or, rarely, melanin (black).
CSF pressure in the lumbar region does not normally exceed 180200 mm water.
Pathologic conditions associated with the increased CSF pressure
include intracranial mass lesions, meningoencephalitis, subarachnoid
hemorrhage, and pseudotumor cerebri.
The CSF normally contains up to five mononuclear leukocytes
(lymphocytes or monocytes) per microliter, no polymorphonuclear
cells, and no erythrocytes. Erythrocytes may be present, however, if
the lumbar puncture is traumatic.
 Normal CSF is sterile, so that in the absence of CNS
infection, no organisms should be observed with the
various stains.
 CSF protein is between 15-45mg/dl .
 CSF sugar is 2/3 blood sugar.
BLOODY CSF
 If the lumbar puncture yields bloody CSF, it is crucial to
distinguish between CNS hemorrhage and a traumatic tap.
 The fluid should be watched as it leaves the spinal needle
to determine whether the blood clears, which suggests a
traumatic tap.
 This can be established with greater accuracy by
comparing cell counts in the first and last tubes of CSF
obtained; a marked decrease in the number of red cells
supports a traumatic cause.
 The specimen should be centrifuged promptly and the
supernatant examined.
 With a traumatic lumbar puncture, the supernatant is
colorless. In contrast, following CNS hemorrhage,
enzymatic degradation of hemoglobin to bilirubin in situ
renders the supernatant yellow (xanthochromic).
 Other causes of CSF xanthochromia include jaundice with
serum bilirubin levels above 4-6 mg/dL, CSF protein
concentrations greater than 150 mg/dL, and, rarely, the
presence of carotene pigments.
ELECTROENCEPHALOGRAPHY
 When the eyes are shut, the most obvious frequency over
the occipital cortex is 8-13/s( alpha rhythm) disappears
when eyes opened.
 Other frequency bands seen over different parts of the
brain in different circumstances are beta (faster than 13/s),
theta (4-8/s) & delta (slower than 4/s).
 Lower frequencies predominate in the very young &
during sleep.
Indications
 Evaluation of suspected epilepsy
 Classification of seizure disorders
 Assessment and prognosis of seizures
 Diagnosis of certain neurologic disorders like herpes
simplex encephalitis, Creutzfeldt-Jakob disease or
subacute sclerosing panencephalitis.
 Evaluation of altered consciousness
Normal EEG
Abnormal EEG
ELECTROMYOGRAPHY AND NERVE
CONDUCTION STUDIES
Indications
 The distinction between disorders primary to nerve or to muscle (neuropathy versus
myopathy).
 The distinction between root or plexus involvement and more distal nerve trunk
involvement.
 The distinction between generalized polyneuropathic processes and widespread




multifocal nerve trunk involvement.
The distinction between upper and lower motor neuron weakness
The distinction, in a given generalized polyneuropathic process, between primary
demyelinating neuropathy and primary axonal degeneration
The assessment, in mononeuropathies, of the site of the lesion and its major effect
on nerve fibers, especially the distinction between demyelinating conduction block
and wallerian degeneration.
The characterization of disorders of the neuromuscular junction.
Imaging
 TECHNIQUES AVAILABLE FOR IMAGING THE NERVOUS SYSTEM
1.
COMPUTED TOMOGRAPHY used for dignosis of stroke, tumor, trauma, SAH
and demenitas
2.
MAGNETIC RESONANCE IMAGING dignosis of stroke, tumor, trauma, SAH,
demenitas, multiple sclerosis and infections.
3.
DIFFUSION-WEIGHTED MAGNETIC RESONANCE IMAGING
4.
PERFUSION-WEIGHTED MAGNETIC RESONANCE IMAGING
5.
POSITRON EMISSION TOMOGRAPHY
6.
SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY
7.
FUNCTIONAL MAGNETIC RESONANCE IMAGING
8.
MAGNETIC RESONANCE SPECTROSCOPY
9.
MAGNETIC RESONANCE ANGIOGRAPHY
10. CT ANGIOGRAPHY
11. PLAIN X-RAYS
12. MYELOGRAPHY
13. ULTRASONOGRAPHY
Right Middle Cerebral Artery Infarction
Left Temporal Tumor
Multiple Sclerosis
BIOPSIES
BRAIN BIOPSY:
 Biopsy of brain tissue can be useful in certain cases when less
invasive methods, such as imaging studies, fail to provide a
diagnosis.
 Brain lesions most amenable to biopsy are those that can be
localized by imaging studies; are situated in superficial,
surgically accessible sites; and do not involve critical brain
regions, such as the brainstem or the areas of cerebral cortex
involved in language or motor function.
 Used for primary and metastatic brain tumors, infectious
disorders such as herpes simplex encephalitis or brain abscess,
and certain degenerative diseases such as Creutzfeldt-Jakob
disease.
MUSCLE BIOPSY:
 Histopathologic examination of a biopsy specimen of a weak muscle
can indicate whether the underlying weakness is neurogenic or
myopathic in origin.
 Examination of a muscle biopsy specimen may also permit certain
inflammatory diseases of muscle, such as polymyositis, to be
recognized and treated.
NERVE BIOPSY:
 evidence may be found of metabolic storage disease (e.g., Fabry
disease, Tangier disease), infection (e.g., leprosy), inflammatory
change, vasculitis, or neoplastic involvement.
ARTERY BIOPSY:
 In patients with suspected giant cell arteritis, temporal artery biopsy
may help to confirm the diagnosis.