Neurologic examination – (El) examen neurológico
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INTRODUCTION
In the day of modern imaging techniques such as computed tomography (CT scan) or magnetic resonance imaging (MRI), the neurologic exam as a diagnostic tool still remains critical in the decision-making process regarding possible intracranial lesions. The neurologic exam allows an astute clinician to pinpoint lesions in the nervous system, often with remarkable accuracy. Because of the length of the visual pathway, which extends from retina to occipital lobe, intracranial lesions often affect some aspect of visual function (Fig. 1).
FIGURE 1. The Visual Pathway
Understanding the basic concepts of the neurologic exam helps the eye care practitioner to identify nervous system abnormalities and their relationships to the visual system. These relationships, along with the patient's history, symptoms, and clinical signs, are key to diagnosing the location and nature of intracranial lesions, which can then be confirmed by radiography, a CT scan, or an MRI.
This course presents a basic neurologic evaluation that could be conducted by an eye care professional. Although there are variations in personal style, emphasis, and order of the tests, most clinicians include certain important procedures in the neurologic exam. The following is a widely accepted format for the neurologic exam, consisting of six subdivisions:
1. Mental Status
2. Cranial Nerves
3. Motor Exam
4. Reflexes
5. Coordination and Gait
6. Sensory Exam
Depending on the clinical situation, certain parts of the exam can be combined, performed in a different order, or performed in greater or less detail. Understanding how to best tailor the exam to the clinical situation comes with both experience and practice.
FIGURE 2. Equipment needed for the neurologic examination.
ASSESSMENT OF PATIENT SIGNS AND SYMPTOMS
Patients may present to the optometrist with no complaints at all or with multiple ocular or neurologic symptoms. The absence or presence of ocular and/or neurologic deficits will determine if the patient should be followed routinely by the optometrist or referred to an appropriate specialist. If no symptoms or signs are present and no ocular or neurologic deficits are discovered, the patient can be followed routinely.
Neurologic symptoms (Table 1) are clues that help to establish the presence of a lesion and must be differentiated from a psychogenic problem or malingering. The most common neurologic symptom that presents to the optometrist's office is headache.
COMMON NEUROLOGIC PROBLEMS
Headache
Speech Problems
Confusion
Tremors
Unsteadiness
Numbness
Visual Symptoms
Weakness
Table 1. Neurologic Symptoms
The optometrist must determine the cause of every symptom and must rule out the presence of disease. If the ocular examination and neurological screening reveal no significant findings, a clinician must decide whether to monitor the patient himself or herself, or refer the patient for further evaluation. Consultation and /or subsequent testing with the primary care physician, internist, ophthalmologist, neuro-eye specialist, neurologist, or endocrinologist can be indicated and can often help to rule out psychogenic symptoms and malingering patients.
Disturbances in the visual pathway may be revealed during the ocular evaluation in the form of decreased visual acuity, pupillary defects, color vision abnormalities, optic nerve problems, or visual field changes detected during perimetry testing.
If a visual pathway defect is discovered, the clinician should attempt to assess the effects of a lesion on neurologic structures near the suspected site. The location of the lesion is determined by its effect on the patient's visual field. Once nearby neurologic structures are identified, the clinician can then infer what potential deficits would occur if surrounding nerves were damaged. If a neurologic defect is discovered during screening, it must be correlated with the relevant neuroanatomy to localize the lesion. CT scans and MR imaging will then help narrow the differential diagnosis. In most of these cases, consultation with a specialist who will oversee the advanced diagnostic and treatment options available to the patient is appropriate. (Fig. 3).
FIGURE 3. Flow chart for the neurologic evaluation of the eye care patient. From Muchnick, B.G. Clinical Medicine in Optometric Practice, St. Louis, 1994, Mosby
THE BASIC NEUROLOGIC SCREENING
The neurologic screening is a series of tests that can be performed on patients within several minutes, or, in some cases, can take up to an hour or more depending on the clinical situation. When performing the neurological evaluation, always consider left to right asymmetry, as well as central vs. peripheral deficits. It is often useful to follow the six subdivisions of a neurologic exam including evaluation of the patient's mental status, cranial nerve function, as well as motor, reflexes, sensory and cerebellar functions. The following describes a basic neurologic evaluation that might be conducted by an optometrist.
EVALUATION OF MENTAL STATUS
The clinician first evaluates alertness, usually while taking the patient's history. Does the patient seem alert and aware? Does she/he seem confused? Is she/he acting in a rational manner? Decreased alertness indicates dysfunction of both cerebral hemispheres or of the reticular activating system of the brainstem. If alertness is sufficient, then it is appropriate to examine and interpret other aspects of the patient's mental status.
To test for orientation and memory, ask for the patient's full name, the location, and the date (often noted as "Alert and oriented to person, place, and time"). Note the exact response. Presenting a set of three common words to the patient and asking him/her to repeat them minutes later can test for short-term memory loss.
For patients with compromised mental status, it is important to document specifically the questions that they were asked and how they were answered. This is the only way to detect changes in mental status when different doctors are following the patient.
Is the patient exhibiting inappropriate emotions, such as laughter or crying? This type of emotional display may be due to bilateral cerebral damage. Is the patient speaking clearly and using vocabulary appropriately? Can the patient understand simple questions and commands? Inability to carry out simple instructions is called dyspraxia and may be due to a deep frontal lobe lesion.
Ask the patient to name some easy objects (e.g., pen, watch, tie) and some more difficult ones (e.g., fingernail, belt buckle). Can the patient close his/her eyes and identify an object by touching it? Inability to do so can indicate a lesion in the non-dominant parietal lobe. Can the patient repeat single words and sentences (a standard is "No ifs, ands, or buts")? These, as well as other kinds of language abnormalities, are usually caused by lesions involving the dominant (usually left) frontal lobe (Broca's Area), and/or the temporoparietal lobe (Wernicke's Area). Multiple deficiencies can signal a global disorder whereas an individual deficit is more likely to signal a more localized lesion.
Table 2 presents the localizing value of the mental status evaluation.
MEDICAL CONDITION DESCRIPTION OF PROBLEM NEUROLOGIC STRUCTURES AFFECTED
Coma Decreased Level of Consciousness Nonlocalizing
Disorientation Lack of Orientation to Time and Place Temporal Lobe
Amnesia Memory Loss Temporal Lobe
Aphasia Speech Problems Frontal, Temporoparietal Lobe
Inappropriate Affect Inappropirate Emotional Display Bilateral Cerebral Damage
Agnosia Inability to recognize Objects Nondominate Parietal Lobe
Apraxia Inability to Follow Orders Frontal Lobe
Table 2. Localizing Value of Mental Status Evaluation. From Muchnick, B.G.: Clinical Medicine in Optometric Practice, St. Louis, 1994, Mosby
CRANIAL NERVE TESTING
Perhaps more than any other part of the neurologic exam, cranial nerve testing can raise red flags that suggest specific neurologic dysfunction rather than a systemic disorder. For example, there are many medical causes of lethargy, unsteadiness, headaches, or dizziness. However, any of these symptoms together with cranial nerve abnormalities strongly suggest brainstem dysfunction as the cause.
The twelve pairs of cranial nerves control the five senses, allow us to interact with the environment, and are necessary for our everyday activities. The cranial nerves may be affected by a wide range of conditions including trauma, infection, cerebrovascular ischemia, space-occupying lesions (such as tumors and aneurysms), and intracranial inflammation.
The cranial nerves are comprised of sensory (afferent), motor (efferent), and mixed (sensory and motor) nerves. Sensory nerves receive information from internal organs, the skin, eyes, ears, and nose. Motor nerves supply innervation to voluntary and involuntary muscles throughout the body. Each cranial nerve can be tested and evaluated in terms of its ability to function. All of the cranial nerve tests can be performed in an optometrist's office.
FIRST CRANIAL NERVE---OLFACTORY NERVE
The olfactory nerve is a special afferent cranial nerve composed of sensory fibers only. Its sole function is to discern smells. Olfaction depends on the integrity of the olfactory neurons in the roof of the nasal cavity and their connections through the olfactory bulb, tract, and stria to the olfactory cortex of the medial frontal and temporal lobes. To test olfaction, an odorant, such as concentrated vanilla, peppermint or coffee extract, is presented to each nostril in turn. The patient is asked to sniff (with eyes closed) and identify each smell (Fig. 4). Olfaction is frequently not tested because of unreliable patient responses and lack of objective signs.
FIGURE 4. Testing the olfactory nerve. While occluding each nostril, patient is asked to sniff and identify various odorants.
SECOND CRANIAL NERVE---OPTIC NERVE
The optic nerve contains special sensory afferent fibers that convey visual information from the retina to the occipital lobe via the visual pathway. Evaluation gives important information about the nerves, optic chiasm, tracts, thalamus, optic radiations, and visual cortex.
CN 2 is also the afferent limb of the pupillary light reflex.
The optic nerve is tested in the office by visual acuity measurement, color vision testing, pupil evaluation, visual field testing, and optic nerve evaluation via ophthalmoscopy and/or stereo biomicroscopy.
Intracranial lesions affecting the visual pathway can be localized based on the pattern of visual field defects. Prechiasmal lesions usually cause monocular field defects. Chiasmal lesions produce heteronymous hemianopsias, and postchiasmal lesions produce homonymous hemianopsias. The further posterior the lesion, the more alike (congruous) the two fields appear.
THIRD CRANIAL NERVE---OCULOMOTOR NERVE
The oculomotor nerve contains somatic efferent and visceral efferent motor fibers. The somatic efferent fibers innervate the levator palpebral superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique muscles of the eye. The visceral efferent fibers convey parasympathetic innervation for pupillary constriction and accommodation (Fig. 5).
FIGURE 5. Testing the optic and oculomotor nerves. The pupillary light reflex
To begin testing CN 3, it is important to first inspect the eyes. Look for ptosis, note the appearance of the eyes, and check for ocular alignment (the light source reflection should fall at the same location on each eyeball).
Next, test extraocular range of motion by having the patient follow a near target through the six principal positions of gaze ("H" pattern). Note any misalignment of the eyes or complaints of diplopia. When specifically evaluating CN 3 during testing, note adduction (medial rectus), depression while abducting (inferior oblique), and elevation (superior rectus and inferior oblique).
Pupillary constriction is tested by the light reflex, and having the patient focus on a near target can test accommodation. Loss of CN 3 function may cause diplopia, and an eye that is "down and out" with ptosis and mydriasis.
FOURTH CRANIAL NERVE---TROCHLEAR NERVE
The trochlear nerve supplies somatic efferent motor fibers that innervate the superior oblique muscle. The superior oblique is tested, as previously described, by inspection followed by having the patient track a near target moved in an "H" pattern (Figs. 6 and 7).
FIGURES 6 and 7. Testing CN III, IV, and VI: To test the extraocular muscles, have the patient follow a target through the six principal positions of gaze ("H" pattern).
Having the patient adduct and look downward to the nose best isolates this nerve. The trochlear nerve is the only nerve to exit from the dorsal aspect of the brain, and it has the longest intracranial course of any cranial nerve. For this reason, it is often the most susceptible to damage from intracranial lesions caused by trauma, inflammatory disease, and compression. Loss of CN 4 function causes diplopia with a compensating head tilt.
FIFTH CRANIAL NERVE---TRIGEMINAL NERVE
The trigeminal nerve supplies both sensory and motor fibers to the face and periorbital area. The afferent sensory fibers separate into three divisions and carry touch, pressure, pain, and temperature sense from the oral and nasal cavities, and the face. Motor efferent fibers function to innervate several facial muscles, including the muscles of mastication.
The sensory portion of the trigeminal nerve is commonly tested by examining the integrity and symmetry of pain and light touch sensation from all areas of the face (forehead, cheek, and jaw). After asking the patient to close his/her eyes, a tissue is lightly touched to one side of the forehead. The tissue is then touched to the opposite side and the patient is asked to compare sensations. A sharp object can be used in the same manner when testing for pain symmetry. The test is then repeated on the cheek (Fig. 8) and jaw line to assess the second and third divisions.
FIGURE 8. Testing the sensory distribution of the trigeminal nerve. Ask the patient to compare the sensation of light touch on both sides of the forehead, cheek, and chin.
An additional test used to evaluate the trigeminal nerve is the corneal reflex test. Evaluate the reflex by gently touching each cornea with a cotton wisp and observing any asymmetries in the blink response (Fig. 9). This tests both the sensory fifth nerve and the motor portion of the seventh nerve, which is responsible for lid closure.
FIGURE 9: The corneal reflex: Immediate closure of both eyelids should occur as examiner touches temporal aspect of cornea with cotton wisp.
To test the motor component of CN 5, feel and compare the tone of the masseter muscles during jaw clench. Next, have the patient open his/her mouth and resist the examiner's attempt to close it. If there is weakness of the pterygoids, the jaw will deviate towards the side of the weakness. Sensory loss of CN 5 is usually due to trauma while vascular damage, tumors, and trauma can result in damage to the motor aspect of the system.
SIXTH CRANIAL NERVE---ABDUCENS NERVE
The abducens nerve supplies somatic efferent motor fibers to the lateral rectus muscle, which functions to abduct the eye. As in prior discussions regarding extraocular muscles, having the patient follow a near target and tracing an "H" pattern tests the abducens nerve. Inability to abduct the eye indicates a possible deficit. Aneurysms, tumors, meningitis, trauma, and cavernous sinus pathology are all potential causes of abducens deficits. Loss of CN 6 function can elicit complaints of horizontal diplopia and may cause patients to appear esotropic.
SEVENTH CRANIAL NERVE---FACIAL NERVE
The facial nerve supplies efferent motor innervation to the muscles of facial expression, and carries sensory afferent fibers from the anterior two thirds of the tongue for taste. To test the motor division of the facial nerve, start from the top and work down. First, have the patient wrinkle the forehead and check for asymmetry (Fig. 10). Next, have the patient shut the eyes tightly while the examiner attempts to open them (Fig. 11). Note any weakness on one side. Finally, have the patient show his/her teeth or smile and compare the nasolabial folds on either side of the face (Fig. 12).
FIGURES 10, 11, and 12. Testing the facial nerve. The patient wrinkles her forehead while the two sides are compared. Patient tightly shuts eyelids while examiner attempts to pry open. The two sides are compared. Patient smiles and shows her teeth while the examiner compares the nasolabial folds on either side.
Bell's palsy is a common lower motor neuron lesion of the facial nucleus or its axon. The result is facial asymmetry with drooping of the eyebrow, a smooth nasolabial fold, drooping of the corner of the mouth, and a reduced blink reflex on the affected side.
To test the sensory fibers of the facial nerve, apply sugar, salt, or lemon juice on a cotton swab to the lateral aspect of each side of the tongue and have the patient identify the taste. Taste is often tested only when specific pathology of the facial nerve is suspected.
EIGHTH CRANIAL NERVE---VESTIBULOCOCHLEAR NERVE
The eighth cranial nerve carries two special sensory afferent fibers, one for audition (hearing) and one for vestibular function (balance). The cochlear division of CN 8 is tested by screening for auditory acuity. This can be done by the examiner lightly rubbing his/her fingers together next to each of the patient's ears and comparing the left and right side responses.
In addition, the Rinne and Weber tests are easy to perform and can help differentiate conductive deficits from neurosensory lesions. The Weber test consists of placing a vibrating tuning fork on the middle of the forehead and asking if the patient feels or hears it best on one side or the other (Fig. 13). The normal patient will say that it is the same on both sides. The patient with unilateral neurosensory hearing loss will hear it best in the normal ear, and the patient with unilateral conductive hearing loss will hear it best in the abnormal ear.
The Rinne test (Fig. 14) consists of comparing bone conduction, assessed by placing the tuning fork on the mastoid process behind the ear, versus air conduction, assessed by holding the tuning fork in air near the front of the ear. Normally, air conduction volume is greater than bone conduction sound volume. For neurosensory hearing loss, air conduction volume is still greater than bone conduction, but for conduction hearing loss, bone conduction sound volume will be greater than air conduction volume.
FIGURES 13 and 14. Testing of the vestibulocochlear nerve. The Weber test. The tuning fork is struck and placed in the middle of the patient's forehead. The patient compares the loudness on both sides. The Rinne test. A tuning fork is held against the mastoid process until it can no longer be heard. It is then brought to the ear to evaluate patient response.
Vestibular testing is can be used to assess brainstem function in comatose patients or in patients who report vertigo/dizziness.
Damage to CN 8 can be caused by trauma, tumors, or infection and can lead to hearing loss, dizziness, loss of balance, tinnitis, and deafness.
(More information on this topic is provided in another Pacific University On-Line CE course: Sensory Conflict and Other Causes of Dizziness: Etiology Differential Diagnosis, and Management by Robert L. Yolton, PhD, OD.)
NINTH CRANIAL NERVE---GLOSSOPHARYNGEAL NERVE
The ninth cranial nerve supplies motor fibers to the parotid gland and the pharynx. It also carries sensory fibers from the carotid body and taste sensation fibers from the posterior third of the tongue.
The gag reflex tests both the sensory and motor components of CN 9 and CN 10. This involuntary reflex is obtained by stroking the back of the pharynx with a tongue depressor and watching the elevation of the palate (as well as causing the patient to gag).
The motor division of CN 9 and CN 10 is tested by having the patient say "ahh" or "kah" (Fig. 15). The palate should rise symmetrically in the back of the oral cavity (Fig. 16). Paralysis of the ninth nerve causes a pulling of the uvula to the unaffected side. The ninth, tenth, and eleventh cranial nerve pathways are physically so close together that isolated lesions are rarely seen.
FIGURES 15 and 16. Testing the glossopharyngeal and vagus nerve. The patient sticks out her tongue and says "ahh." The palate and uvula should elevate symmetrically without deviation.
TENTH CRANIAL NERVE---VAGUS NERVE
The vagus nerve carries sensory afferent fibers from the larynx, trachea, esophagus, pharynx, and abdominal viscera. It also sends efferent motor fibers to the pharynx, tongue, thoracic and abdominal viscera, and the larynx. Testing of the vagus nerve is performed by the gag reflex and "ahh" test as described above.
A unilateral lesion affecting the vagus nerve can produce hoarseness and difficulty swallowing due to a loss of laryngeal function. Causes of unilateral lesions include trauma from surgical procedures of the neck, aortic aneurysm, and compression due to enlarged paratracheal lymph nodes caused by metastatic carcinoma.
ELEVENTH CRANIAL NERVE---ACCESSORY NERVE
The accessory nerve carries efferent motor fibers to innervate the sternomastoid and trapezius muscles. The accessory nerve is tested by asking the patient to shrug the shoulders (trapezius muscles) and turn the head (sternomastoid muscles) against resistance (Figs. 17 and 18). Palpate the patient's sternocleidomastoid muscles and feel for tension as the patient attempts to turn his/her head.
FIGURES 17 and 18. Testing the accessory nerve. Patient is instructed to shrug their shoulders against resistance. The patient turns her head against the examiner's hand while the sternomastoid muscle is palpated. The muscle tone on both sides is compared.
Loss of CN 11 function causes a drooping of the ipsilateral shoulder and trapezius on the affected side. The patient may also have difficulty turning his head to the side opposite the lesion. Damage usually occurs secondary to surgery or trauma.
TWELFTH CRANIAL NERVE---HYPOGLOSSAL NERVE
The twelfth cranial nerve supplies efferent motor fibers to the muscles of the tongue. To test the hypoglossal nerve, have the patient stick out their tongue and move it side to side. If there is unilateral weakness, the protruded tongue will deviate towards the side of the weakness.
Further testing includes moving the tongue right to left against resistance (Fig. 19), or having the patient say "la, la, la."
FIGURE 19. Testing the hypoglossal nerve. Patient is instructed to stick out the tongue and then move it laterally against resistance.
Summary of Cranial Nerve Functions
Table 3 summarizes the cranial nerves and their functions.
Cranial Nerve Number Innervation(s) Primary Function(s) Test(s)
Olfactory I Sensory Smell Identify odors
Optic II Sensory Vision Visual acuity, fields, color, nerve head
Oculomotor III Motor Upper lid elevation, extraocular eye movement, pupil constriction, accommodation Physiologic "H" and near point response
Trochlear IV Motor Superior oblique muscle Physiologic "H"
Trigeminal V Motor Muscles of mastication Corneal reflex
Trigeminal V Sensory Scalp, conjunctiva, teeth Clench jaw/palpate, light touch comparison
Abducens VI Motor Lateral rectus muscle Abduction, physiologic "H"
Facial VII Motor Muscles of facial expression Smile, puff cheeks, wrinkle forehead, pry open closed lids
Facial VII Sensory Taste-anterior two thirds of tongue
Vestibulocochlear VIII Sensory Hearing and balance Rinne test for hearing, Weber test for balance
Glossopharyngeal IX Motor Tongue and pharynx Gag reflex
Glossopharyngeal IX Sensory Taste-posterior one third of tongue
Vagus X Motor Pharynx, tongue, larynx, thoracic and abdominal viscera Gag reflex
Vagus X Sensory Larynx, trachea, esophagus
Accessory XI Motor Sternomastoid and trapezius muscles Shrug, head turn against resistance
Hypoglossal XII Motor Muscles of tongue Tongue deviation
Table 3: Cranial Nerves Summary. From Muchnick, B.G.: Clinical Medicine in Optometric Practice, St. Louis, 1994, Mosby
EVALUATION OF MOTOR FUNCTION
Evaluation of the motor system is divided into the following components.
1. Observation
2. Inspection
3. Palpitation
4. Muscle tone testing
5. Functional testing
6. Strength testing of individual muscle groups
The first step in evaluating a patient's motor system involves careful observation of the patient. In addition to posture, note any twitches, tremors, or involuntary movements. Next, inspect several individual muscles to see if muscle wasting, hypertrophy, or fasciculations (spontaneous quivering movements caused by firing of muscle motor units) are present. In cases of suspected myositis, it is appropriate to palpate the muscles to check for tenderness.
To assess muscle tone, ask the patient to relax, and then passively move each limb at several joints to evaluate any resistance or rigidity that may be present.
Functional testing can often help to detect subtle abnormalities. For example, drift can be assessed by having the patient close his/her eyes and extend both arms to the front with palms up. Observe the arms to determine if one or both drift downward to side. It is also possible to assess the patient's fine movement control by asking him/her to make rapid hand movements or tap a foot rapidly.
Finally, during a complete neurologic examination, test the strength of each muscle group and record it in a systemic fashion (Table 4).
Table 4. Rating Scale for Evaluation of Muscle Strength. From Stephen Russell, Marc Triola. The Precise Neurological Exam. NYU School of Medicine
Although muscle weakness is a fairly non-localizing finding that can be caused by disturbances in several aspects of the nervous or muscular systems, many components of the motor exam can help to distinguish between upper motor and lower motor neuron lesions (Table 5).
Table 5. Signs of Upper and Lower Motor Neuron Lesions. From Blumenfeld, An Interactive On-Line Guide to the Neurologic Examination.
To screen for muscle weakness, perform tests that will assess both upper and lower extremity strength (Fig. 20). For example, have the patient flex and extend both arms and legs against resistance. Record any weakness of one limb when compared to the contralateral limb.
FIGURE 20. Evaluation of motor function. Asking the patient to raise both arms in front of them while the examiner provides resistance tests upper extremity muscle strength.
EVALUATION OF REFLEXES
A neurologic exam should include an evaluation of reflexes. Examples can include deep tendon reflexes (patellar tendon), plantar response (Babinski's sign), and finger flexors (Hoffmann's sign). When testing, note that reflexes can be influenced by age, metabolic factors such as thyroid dysfunction or electrolyte abnormalities, and anxiety of the patient.
Of the many reflex tests to choose from, the patellar tendon (knee-jerk) reflex test is commonly used. To perform this test, have the patient sit on the edge of a table or chair and dangle the feet. The examiner's hand is placed on the patient's quadriceps muscle and the patellar tendon is struck with a reflex hammer. It should be possible to feel the quadriceps contract and the knee extend when the patellar tendon is struck (Fig. 21). Certain cerebellar injuries can result in abnormal knee-jerk responses. Loss of deep tendon reflexes can also be associated with Adie's tonic pupil and reflex tests are mandatory in patients presenting with light-near dissociation pupils.
FIGURE 21: Evaluation of deep tendon reflexes. With the lower leg hanging freely off the end of the chair, the "knee-jerk" reflex is tested by striking the patellar tendon directly with the reflex hammer.
EVALUATION OF COORDINATION AND GAIT
Examinations of coordination and gait are used for testing cerebellar function (the cerebellum coordinates muscle actions to produce organized activities such as walking). To test coordination, evaluate the patient's ability to perform rapidly alternating and point-to-point movements. For example, ask the patient to place her/his hands on their thighs and then rapidly turn the hands over and lift them off the thighs. Once the patient understands this movement, tell him/her to repeat it rapidly for 10 seconds.
Next, the examiner can hold his/her index finger at arms length from the patient. The patient is asked to touch his/her own nose with their index finger (Fig. 22) and then to touch the examiner's finger (Fig. 23). This movement is repeated several times with the patient's eyes open and then with them closed. Nose to finger touching is an example of a point-to-point movement. A patient with a disorder of the cerebellum tends to overshoot the target (past pointing).
FIGURE 22 and 23. Evaluation of cerebellar function. While the examiner holds his finger at arm's length from the patient, the patient touches her nose and then touches the examiner's finger. After several sequences, the patient is asked to repeat the exercise with her eyes shut. A patient with a cerebellar disorder tends to overshoot the target.
Gait can be evaluated by having the patient walk across the room under observation. Watch for normal posture and coordinated arm movements. Next, ask the patient to walk heel to toe (Fig. 24) across the room, to walk on their toes to test for plantar flexion weakness, and finally to walk on their heels to test for dorsiflexion weakness. Abnormalities in heel to toe walking may be due to ethanol intoxication, weakness, poor position sense, vertigo, and/or leg tremors. These causes must be excluded before poor balance can be attributed to a cerebellar lesion. Most elderly patients have difficulty with tandem gait (heel to toe walking) due to general neuronal loss impairing a combination of position sense, strength, and coordination.
FIGURE 24. Examination of gait. Heel to toe walking (tandem gait)
Another convenient test for cerebellar function is the Romberg test. Have the patient stand with heels and toes together. Ask the patient to remain still and close their eyes. To achieve balance, a person requires at least two out of three of the following: 1) visual confirmation of position, 2) non-visual confirmation of position (including proprioceptive and vestibular input), and, 3) a normal functioning cerebellum. Therefore, if a patient loses balance after standing still with their eyes closed, but maintains balance with their eyes open, then there is likely to be a lesion in the cerebellum. This is a positive Romberg test (Fig. 25).
FIGURE 25. The Romberg test. Have the patient stand still with heels and toes together. Ask the patient to close her eyes and balance herself. If the patient loses her balance, the test is positive.
EVALUATION OF SENSORY FUNCTIONS
The neurologic evaluation should include tests for the primary senses of touch, pain, and vibration. Causes of sensory disturbances include diabetes mellitus, thiamine deficiency, neurotoxin damage, and spinal cord lesions. Affected patients can report paresthesias (pins and needles), dysesthesias (pain), as well as sensory loss, usually in the hands and feet.
To evaluate tactile sense, the patient's fingers and toes are lightly touched with a tissue (Fig. 26). With their eyes closed, patients are asked to identify when they feel the stroke of the tissue.
FIGURE 26. Evaluation of tactile sense. The patient is asked to close her eyes while fingers and toes are lightly touched with a tissue.
To test for pain sensation, touch the patient on the fingers and hand with a safety pin (Fig. 27). Alternate the sharp tip with the blunt end (Fig. 28) to determine whether the patient can discern the difference between sharp and dull sensations. Repeat this test on the patient's toes.
FIGURE 27 and 28. Evaluation of pain sense. Patient is asked to close her eyes. The examiner randomly alternates touching the patient (fingers and toes) with the sharp and dull ends of a paper clip (or safety pin) while the patient identifies the stimulus.
Vibration sense is tested by striking a tuning fork and placing it over the base of the nail bed on the patient's index finger. The examiner should place his/her index finger under the patient's to feel the vibration. Ask the patient when he/she no longer feels the vibration. For each test, comparison should be made from one side of the body to the other on each extremity. A significant finding during testing is a marked decrease in sensitivity.
CONCLUSIONS
The neurologic exam remains a valuable tool for the detection of intracranial lesions and nervous system disorders. Mastering the neurologic exam and utilizing its value takes practice, experience and a basic understanding of neuroanatomy. As the scope of optometry continues to grow, optometrists must continue to expand their knowledge to meet the needs of the primary care patient. This knowledge enables optometrists to co-manage and communicate with primary care physicians, as well as other healthcare specialists, and to better participate as a member of the medical community.
REFERENCES
Muchnick, BG.: Clinical Medicine in Optometric Practice, St Louis, 1994, Mosby.
Lee, DA, Higginbotham, EJ: Clinical Guide to Comprehensive Ophthalmology, New York, 1999, Thieme.
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Leigh RJ, Zee, DS: The Neurology of Eye Movements, Philadelphia, 1991, F. A. Davis Co.
Weiner WJ, Goetz CG, editors: Neurology for the Non-Neurologist, Philadelphia, 1981, Harper and Row.
Hurst LP, editor: Medicine for the Practicing Physician, 4th edition, Stamford, Conn., 1996, Appleton & Lange.
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