Neurological diagnostic procedures

Neurological diagnostic proceduresGeneral physical examination and medi­cal history may give insight to a neurological disease by notation of pain, alterations of sensa­tions, motion and gait disturbances, muscular weaknesses and degenerations, musclc spasms, and mental changes.

Neurological examination includes testing of the special senses, muscle functions, and re­flexes. Testing of the special senses (smell, sight, hearing, taste, equilibrium, etc.) may give insight to a disorder of a cranial nerve. Skin testing over the entire body for the accuracy to perceive sensations may provide evidence of nervous system disorder. Testing for the pres­ence or absence of the conscious reflexes may de­note disease of the nervous system.

Reflexes which may be outwardly induced and which may be useful for diagnosis may be classified as superficial, deep, visceral, and pathological. Some of the more common reflexes tested in neurological examination are:

Superficial reflexes—those where there is a reac­tion from stimulating the skin or a mucous membrane.

  1. Conjunctival—gentle irritation of conjunctiva causes eye to blink.
  2. Nasal—irritation of nose lining causes sneez­ing.
  3. Gag—irritation of pharynx causes gagging.
  4. Abdominal—irritation of skin on abdomen causes abdominal muscles to contract.
  5. Cremasteric—irritation of skin on thigh causes testicle to elevate.
  6. Plantar—irritation of sole of foot causes foot to arch or withdraw.

Deep reflexes—those where striking a tendon causes a muscle to contract.

  1. Biceps—tap on bicep tendon causes elbow to flex.
  2. Triceps—tap on tricep tendon causes elbow to extend.
  3. Wrist—tap on forearm muscle causes wrist to flex or extend.
  4. Patellar—tap below kneecap causes knee to extend.
  5. Achilles—tap on heel causes ankle to flex. Visceral reflexes—those where stimulating an or­gan causes that organ or another organ to react.
  6. Pupil—light shone in eye causes pupil to con­strict.
  7. Accommodation—object moved toward eye causes pupil to constrict and eyes to converge.
  8. Oculocardiac—pressure on eyeball causes heart rate to slow.
  9. Carotid—pressure on neck artery causes heart rate to slow and blood pressure to lower.

Pathological reflexes—abnormal reflexes found in disease states.

Reflexes which over-respond are said to be hyperactive, and those which are dulled are called hypoactive; or a reflex may be referred to as absent.

All neurological signs and symptoms have to be correlated to ascertain the nature and loca­tion of a neurological disorder.

The electroencephalogram (EEG) is a graph of the electrical impulses of the brain. During nervous metabolism minute electrical currents are perpetually produced, so in effect the human brain is actually a battery. Delicate instruments can pick up these currents. The electroencephalogram is such an instrument, which makes the graph recording from various sites over the skull. For this, minimal but pre­cise preparation is required. Electrodes are placed at various sites over the head and a tech­nician procures the recording. The procedure is entirely painless.

EEG’s are interpreted by a neurological spe­cialist who correlates the various waves with the signs and symptoms of the patient. This is a valuable diagnostic tool in cases of brain dis­ease, both organic and functional.

The spinal tap, or lumbar puncture, has been described. In any case where a central nervous system disease is suspected, this test is indicated. To re-emphasize, the com­plications from spinal tap are nil, despite various ill-conceived notions in some communities. The discomfort associated is slight.

The cisternal puncture is another means of obtaining a sample of the cerebrospinal fluid. The procedure involves insertion of a needle (under local anesthesia) into the upper neck at the base of the skull where there is a relatively large cavity of fluid (cisterna magna) between the lining dura mater and the cerebellum. This procedure is quite similar to the spinal puncture and is frequently indicated in conditions where there is thought to be some disparity between the two levels of fluid.

The ventricular puncture is the withdrawal of fluid from one of the cerebral ventricles. In this procedure a needle is inserted through the scalp and skull down through the cerebrum into a ventricle. This procedure is not painful under local anesthesia, and may be of extreme value whenever there is suspected a block or disparity between the ventricle fluid and that of lower levels.

X-ray procedures may greatly contribute to a neurological diagnosis. Besides the usual x-ray plates of the bony skull and spinal col­umn, various special procedures are often em­ployed. The myelogram (cord-study) is a technique whereby a solution opaque to x-ray is injected into the spinal canal to outline its inner contours. This necessitates spinal puncture. The solution is instilled and the patient is positioned and tilted to allow it to pass up and down the spinal canal while it is observed by fluoroscopy. X-ray plates at vari­ous levels arc taken. Abnormalities such as tu­mors, injuries, spinal disc protrusions, and con­genital defects may be seen.

The pneumoencephalogram (air-brain- study) is another special x-ray procedure, in which the cerebrospinal fluid is removed by spinal puncture and replaced by air. This out­lines the central nervous system spaces as the air acts as a contrast media on x-ray. Outline of the ventricles is referred to as a ventricu­logram. In this technique the cerebrospinal fluid is removed from the ventricles by ventricu­lar puncture and replaced by air or oxygen. This is an operating room procedure.

The angiogram (vessel-study) is an x-ray exposure of the head after the injection of an opaque solution into an artery in the neck, usu­ally the carotid artery. The contrast media is injected through a needle inserted into the ar­tery (closed angiography), or the vessel may be operatively dissected out for instilling the media (open angiography). As soon as the injection is completed, immediately x-ray plates are made; these outline the vessels in the head. This procedure will outline any abnormalities of the vessels or displacement of the vessels by such things as tumor or blood clot.

The various x-ray procedures to be employed will depend on the nature and location of the disease suspected.

Electrical stimulation of nerves at their various motor-points to muscles may be use­ful in the diagnosis of nerve injuries and dis­eases. In this examination the nerves are stimu­lated by electrical current (galvanic or faradic current). Normally the muscles supplied by the nerve will contract as the impulse passes down the nerve. Loss of such muscular reaction dem­onstrates a paralysis of the nerve; such may be due to a severance of the nerve from injury or failure of the nerve to conduct impulses from any cause. This test serves as an aid in both the diagnosis and the prognosis of nerve lesions.

Nerve block is a diagnostic procedure wherein the area about a nerve is infiltrated with a local anesthetic which blocks its impulses. Thereby the effects of such temporary paralysis of a nerve may be studied. In certain cases of severe intractable pain the results of permanently paralyzing a nerve may be anticipated. In other instances observation of the motor function of nerves can be evaluated.

The sympathetic block is a special type of nerve block in which the sympathetic trunk is anesthetized. This is a useful tool in the study of blood vessel diseases, especially of the lower extremity. In this instance the injection is made in the mid-back region alongside the spinal col­umn. Observation of the circulation status is made before and after paralyzing the sympa­thetic trunk. On the basis of such changes in the temperature, pain, and color of the foot and leg on the injected side, the value and effects of disrupting the sympathetic trunk (by the opera­tion sympathectomy) may be evaluated.

Use of nerve blocks for treatment purposes are hereinafter mentioned.

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