Neurologic InvestigationsDr. Hawar Adnan Mykhan

M.B.Ch.B., F.I.B.M.S

INVESTIGATION OF NEUROLOGICAL DISEASE1. CLINICAL NEUROPHYSIOLOGYa) Electroencephalography (EEG)b) Electromyography, Nerve conduction studies and repetitive

nerve stimulation (EMG, NCS, RNS)c) Evoked potentials (EP)2. IMAGING3. SPECIAL TESTSa) Blood testsb) CSF analysisc) Biopsies

CSF analysisIndications

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.

ContraindicationsSuspected 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.

ComplicationsUNSUCCESSFUL 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 ResultsCSF is normally clear and colorless.It may appear cloudy or turbid with white blood cell counts that exceed about

200/μLColor 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 180- 200 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 CSFIf 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.

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ELECTROENCEPHALOGRAPHYWhen 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 epilepsyClassification of seizure disordersAssessment and prognosis of seizuresDiagnosis 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 demenitas2. MAGNETIC RESONANCE IMAGING dignosis of stroke, tumor, trauma, SAH, demenitas,

multiple sclerosis and infections. 3. DIFFUSION-WEIGHTED MAGNETIC RESONANCE IMAGING4. PERFUSION-WEIGHTED MAGNETIC RESONANCE IMAGING5. POSITRON EMISSION TOMOGRAPHY6. SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY7. FUNCTIONAL MAGNETIC RESONANCE IMAGING8. MAGNETIC RESONANCE SPECTROSCOPY9. MAGNETIC RESONANCE ANGIOGRAPHY10. CT ANGIOGRAPHY11. PLAIN X-RAYS12. MYELOGRAPHY13. ULTRASONOGRAPHY

Right Middle Cerebral Artery Infarction

Left Temporal Tumor

Multiple Sclerosis

BIOPSIESBRAIN 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.