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- Assessment of Patient Signs and Symptoms
- The Basic Neurologic Screening
- Evaluation of Mental Status
- Cranial Nerve Testing
- Evaluation of Motor Function
- Evaluation of Reflexes
- Evaluation of Coordination and Gait
- Evaluation of Sensory Functions
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
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.
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
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 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.
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|