What You Forgot About the Neurologic Exam, Part 1:

December 1, 2004
Silvana Riggio, MD
Silvana Riggio, MD

,
Andy Jagoda, MD
Andy Jagoda, MD

ABSTRACT: When you approach a patient with a neurologic complaint, look for abnormal postures and bodily asymmetries. Careful history taking puts the patient's complaint in context and gives direction to the clinical investigation. Remember that a change in the character of an existing condition requires assessment as a new complaint. The mental status evaluation, at a minimum, considers the patient's level of alertness and orientation, including speech and comprehension. Distinguish among delirium, dementia, and psychosis, and avoid making a psychiatric diagnosis until organic causes have been excluded. Cranial nerves II to VIII are the most pertinent to the neurologic screening examination. The evaluation of cranial nerves II, III, IV, and VI is particularly important in patients with headache or visual disturbances and suspected intracranial lesions.

Advances in the management of neurologic disorders have augmented the importance of the screening evaluation. Interventions that can significantly reduce morbidity and mortality are often time-sensitive. Examples are thrombolytic therapy for stroke1,2; use of anticonvulsants for nonconvulsive and subtle, generalized status epilepticus3; and plasmapheresis for Guillain-Barré syndrome.4

Properly organized, a neurologic screening assessment can be completed within minutes.5 When you first approach the patient, look for abnormal postures and bodily asymmetries. Ascertain the chief complaint and its history. Attend systematically to the 6 major focuses of the neurologic examination:

•Mental status.

•Cranial nerves (CNs).

•Motor function.

•Reflexes.

•Sensory status.

•Coordination and balance.

In this article, we outline a basic screening examination, which provides a framework for you to build on. You can pursue some points further by consulting an appropriate reference.5-8 Here we discuss the essentials of the history taking and the mental status and CN assessments. In a forthcoming issue, we will discuss the evaluation of motor function, reflexes, sensory status, and coordination and balance. In both parts, to stimulate thought and illustrate central concepts, we describe cases that we have encountered.

HISTORY

The patient's chief complaint often serves to direct the examination; take care, however, not to let bias be introduced. A patient with subarachnoid hemorrhage may complain of "a migraine," or one with Guillain-Barré syndrome, of "the flu."9 A careful inquiry into the history provides clues to the cause of the patient's problem and can guide diagnostic testing. For example, your questioning of an alert patient with a headache elicits a report of associated neck pain that started after a car accident; the examination and radiographic imaging may then focus on carotid or vertebral artery dissection.10

The history taking begins with a clear definition of the patient's complaint: you need to differentiate vertigo from dizziness, blindness from decreased vision, weakness from fatigue. Family members or bystanders are often able to place the complaint in the context of associated events.

Key points in the history include time of onset, mode of onset, progression, factors that ameliorate or exacerbate the symptoms, and previous occurrences of similar problems. For example, the abrupt onset of a neurologic complaint suggests a vascular event that requires immediate attention. The patient's medical history, occupation, medications, or illicit drug use also may give clues to the diagnosis or have a bearing on therapy. Table 1 shows which elements of the history and physical examination are especially pertinent to various common neurologic complaints.

CASE 1: WOMAN WITH SEVERE HEADACHE

The case. A 46-year-old woman presented with a severe headache, which had begun 12 hours earlier. She had a history of monthly migraine headaches without aura that she described as being on one side, throbbing, and accompanied by nausea and vomiting. She visited the emergency department (ED) 3 or 4 times a year for refractory episodes.

She had taken 500 mg of naproxen, without relief. By her description, the present headache was similar in intensity to past ones but different in location, since it was on both sides and radiated to the back of the head. A neurologic examination was deferred because the patient was uncomfortable and the diagnosis appeared evident to the treating physician.

The patient was given prochlorperazine, 10 mg IV, and the headache resolved. She was discharged with instructions to consult her private physician. Eighteen hours later, she was found to be unresponsive by her family and was brought to the ED by emergency medical services. A noncontrast head CT scan revealed subarachnoid bleeding (Figure 1). The patient had a complicated hospital course and died 8 days later.

Commentary. In this case, two fundamental points stand out:

A change in the clinical presentation of an existing condition requires an evaluation as if the patient had a new complaint. In this case, the patient clearly stated that her headache was different from past headaches. Therefore, the differential diagnosis was open. The decision to treat with prochlorperazine, a serotonin receptor modulator, was appropriate for acute control of a severe migraine headache (although this is not a labeled indication for the drug); however, prochlorperazine will attenuate headache pain regardless of its cause.11

A patient with a neurologic complaint requires a neurologic examination. When the complaint is headache, the examination focuses on CNs II, III, IV, and VI. In this case, it might have revealed a dilated pupil. The most common cause of subarachnoid hemorrhage is a ruptured cerebral aneurysm,12 and a common aneurysm site is the posterior communicating artery, next to CN III. Compression of CN III results in parasympathetic dysfunction and, hence, dilation of the pupil.

MENTAL STATUS

The neurologic examination begins with assessment of mental status. At a minimum, you need to assess the patient's level of alertness and orientation, with attention to speech and comprehension. A basic determination uses the "A, V, P, U" method:

•A, alert.

•V, responsive to verbal stimuli or commands.

•P, responsive to painful stimuli only.

•U, unresponsive.

Often, changes in mental status are subtle and not obvious to the examining physician. Give careful consideration to concerns expressed by family members.

The Glasgow coma scale was developed as a prognostic tool for patients with traumatic brain injury.13 The score is calculated from the best eye-opening response (1 to 4), verbal response (1 to 5), and motor response (1 to 6); a score of 3 is consistent with coma and a score of 15, with minor or no trauma-related dysfunction. The Glasgow coma scale is not useful in evaluating patients with metabolic or toxic conditions.

Delirium, dementia, and psychosis are differentiated by the clinical features listed in Table 2. A systematic assessment of mental status is helpful in diagnosing acute processes in patients with chronic disease, such as delirium in a patient with dementia. The confusion assessment method was developed to assist in diagnosing delirium.14 It assesses 4 components: acute onset, fluctuating course, inattention, and disorganized thinking or an altered level of consciousness.

The "mini-mental state" examination is reserved for patients with suspected cognitive dysfunction.15,16 In essence, it evaluates 5 areas: orientation, registration, attention, recall, and language.

CASE 2: "ODD" BEHAVIOR IN AN OLDER MAN

The case. A 78-year-old man was brought to the ED by his family, who described him as "not acting himself." The patient had hypertension but otherwise was in excellent health. Two days earlier, he had begun to behave in a way that struck his family as odd and to express paranoid ideations. On the day of admission, he had tried to leave his apartment, claiming that someone was trying to hurt him.

The patient was taking nifedipine and one "baby aspirin" a day. He had no history of psychiatric illness. His blood pressure was 148/92 mm Hg; heart rate, 82 beats per minute; and respiratory rate, 16 breaths per minute. His skin was warm and dry. The blood glucose level, measured with a finger-stick test, was 110 mg/dL.

The patient appeared comfortable and willing to respond to questions. He was alert and oriented to person, place, and time, but his answers were slow and he appeared distracted. (According to his family, this was very unlike his usual manner.) The results of physical and neurologic examination were recorded as normal, and the patient was admitted to a psychiatric unit with a diagnosis of psychosis.

Three days later, the patient experienced a brief, generalized tonic-clonic seizure, after which he returned to the baseline established at admission. A neurology consultation was obtained, and it was noted that the patient had subtle, intermittent lip-smacking. A bedside electroencephalogram (EEG) was obtained, and a diagnosis of nonconvulsive status epilepticus (NCSE) was made. The patient was given lorazepam, 2 mg IV, with normalization of the EEG and complete resolution of his abnormal behavior.

Commentary. This case demonstrates the importance of carefully considering concerns expressed by family members, of evaluating patients with altered behavior for organic causes before prematurely diagnosing a psychiatric disorder, and of considering NCSE as a cause of altered mental status.

Like convulsive status epilepticus, NCSE results from either a primary generalized process (absence status), or a secondary generalized process (complex partial status). Its hallmark is altered mental status, and the diagnosis can easily be missed. Patients in NCSE may appear totally functional and be able to perform complex tasks, such as driving a car.

Other possible alterations are speech arrest, cognitive deficits, delusions, paranoia, hallucinations, and psychosis. Disturbances in speech patterns are frequent, ranging from verbal perseveration to aphasia.17 Abnormal motor activity, such as automatism, is rarely the predominant clinical finding in NCSE, although when present, it may point to the correct diagnosis.

Many patients in NCSE, presenting with altered mental status, have initially been deemed to have a psychiatric problem. Only later was the true diagnosis made, either by means of the EEG or after the onset of a convulsive component.18-21

There appears to be a distinct subgroup of patients in whom NCSE develops in later life, as a result of metabolic abnormalities or drug withdrawal, or idiopathically.20,22 NCSE is reported to be very responsive to the benzodiazepines, either diazepam or lorazepam.19 EEG confirmation is recommended before pharmacologic intervention.

CRANIAL NERVES

In general, CNs II to VIII are the most pertinent in the neurologic screening examination; testing the other CNs is complaint-based. Evaluation of CNs II, III, IV, and VI is especially important for patients with headaches or visual disturbances and suspected intracranial lesions.

CN II. Testing the optic nerve involves visual acuity (central vision), gross visual fields (peripheral vision), and the ophthalmoscopic examination. Visual acuity must be checked individually in each eye. Changes in visual acuity result from either refractive error or optic nerve dysfunction; the former is corrected with a pinhole test, while the latter is not.

The swinging-flashlight test (discussed below, under CN III) provides information on optic nerve function. Peripheral vision is checked in a visual field examination; each eye is tested individually with the confrontation method. Blindness in one eye suggests a lesion in front of the optic chiasm; bitemporal hemianopia suggests a lesion at the chiasm; a quadrant deficit suggests a lesion in the optic tracts; and bilateral blindness suggests cortical disease.

The ophthalmoscopic examination evaluates the optic disc, retinal arteries, and retinal veins. Signs of papilledema include blurring of the lateral margin of the optic disc, loss of blood vessels as they cross the edematous disc, distended veins, and loss of venous pulsations.

CNs III, IV, and VI. CN III innervates the extraocular muscles, primarily effecting adduction and vertical gaze. It is tested in conjunction with CN IV, which aids in internal depression via the superior oblique muscle, and CN VI, which controls abduction via the lateral rectus muscle.

Test extraocular muscle function by holding a pen vertically in front of the patient. Instruct the patient to follow with his eyes while you move the pen horizontally and to tell you how many pens he or she sees; split images suggest diplopia. Repeat this procedure in the horizontal plane. Diplopia requires binocular vision and resolves when one eye is occluded. (Lens dislocation or retinal detachment can cause distorted but not split images.)

While checking the extraocular movements, look for nystagmus. Slight nystagmus on extreme lateral gaze may be normal. Marked nystagmus on lateral gaze or any nystagmus on vertical gaze is abnormal and suggests a peripheral or CNS lesion. Vertical nystagmus is seen with brain stem lesions or phencyclidine intoxication. Pendular nystagmus (with equal to-and-fro movements) is usually congenital.

The pupillary light reflex is mediated by the parasympathetic nerve fibers that lie outside CN III.23 Test the pupillary response by shining a light into each eye individually. In the swinging-flashlight test, a light is passed from one eye to the other. When the light shines directly into a normal eye, both eyes constrict via the direct light response and the consensual light response. A Marcus Gunn pupil, one that constricts via the consensual response but dilates when light shines directly into it, indicates an afferent nerve defect. This is seen in optic nerve disease-for example, in multiple sclerosis.

Observe and document pupil size. Asymmetry of less than 1 mm is of no pathologic significance. A larger difference suggests CN III compression; this can be caused by aneurysms or, in patients with altered mental status, by cerebral herniation.

Bilateral pupil dilation is caused by prolonged anoxia or by drugs (anticholinergic or adrenergic agents). Unilateral pupil constriction results from sympathetic chain dysfunction-for example, in Horner syndrome or with carotid artery dissection. Bilateral pupil constriction is seen with pontine hemorrhage or is caused by drugs or toxins (such as opiates, clonidine, and organophosphates).

CN V. The trigeminal nerve has both sensory and motor function. A CNS lesion affecting CN V usually involves all 3 of its branches, making individual testing unnecessary. Sensory function is most reliably tested with double simultaneous stimulation (to be discussed under "Sensory status" in part 2 of this article). CN V also supplies the muscles of mastication, which are tested by palpating the masseter muscles while the teeth are clenched.

CN VII. The facial nerve innervates motor fields in the anterior scalp and face, as well as sensory fields in the anterior two thirds of the tongue, in the ear canal, and behind the ear. Weakness is often apparent as a facial droop or flattening of the nasolabial fold. More subtle weakness becomes apparent when you ask the patient to show his teeth or to whistle.

Central lesions cause contralateral weakness of the face below the eyes. The forehead is spared because of the crossing of central fibers; thus, with central lesions, the eyebrows can be elevated and the eyes tightly closed. Patients with peripheral CN VII lesions, including Bell palsy, may have a complete facial weakness that includes the forehead. Since isolated central CN VII lesions are rare, absence of brow and forehead involvement does not necessarily indicate a central lesion, especially if the patient is otherwise neurologically intact.

CN VIII. The acoustic nerve has a vestibular and a cochlear component. The vestibular nerve supplies the semicircular canals, and the cochlear nerve supplies the Corti organ (which contains receptors for hearing). Decreased hearing is caused by either a conductive defect (for example, wax in the ear canal) or a sensorineural defect. An easy screening test for hearing defects involves asking the patient to hum. With conductive defects, the hum is louder in the affected ear. With sensorineural defects, the normal ear hears the louder hum.

When you suspect a vestibular nerve defect, assess the patient for nystagmus and perform a Nylen-Barany maneuver. This rapidly takes the patient from a sitting position to a supine one in which the head lies 45 degrees below the horizontal. Repeat the maneuver with the patient's head turned 30 to 45 degrees to the right and then to the left. A positive result, namely, onset of nystagmus, reproduction of vertigo, or both, suggests a peripheral cause of vertigo. The nystagmus of peripheral vertigo has a brief latency before onset, is suppressible by visual fixation, is fatigable, and worsens with changes in position. That of central vertigo has immediate onset and is not suppressible, fatigable, or positional.

CASE 3: MAN WITH DIPLOPIA AND HEADACHE

The case. A 38-year-old man complained of double vision when he looked to the left. He reported a dull, persistent frontal headache that had been present for 2 months. He denied fevers, nausea or vomiting, weakness, and fatigue. He had no significant medical history and was not taking any medications.

On physical examination, the patient appeared comfortable and had stable vital signs. His pupils were equal and reactive to light; the fundi were not visualized. There was no ptosis; CNs III and IV were intact; and on left lateral gaze, the left eye did not move past the midline (Figure 2). A noncontrast head CT scan was normal.

A neuro-ophthalmologic consultation was obtained to evaluate the patient's CN VI palsy. His pupils were dilated, and the funduscopic examination revealed papilledema (Figure 3). A lumbar puncture was performed with an opening pressure of 260 mm H2O and otherwise normal results of cerebrospinal fluid (CSF) analysis. Idiopathic intracranial hypertension (IIH) was diagnosed.

Commentary. This case illustrates the importance of the CN assessment for patients who complain of headache or visual disturbances; ophthalmoscopy is an important component of the assessment. In this case, the finding of papilledema associated with a normal CT scan led to the correct diagnosis. The diagnos- tic features of IIH (once termed "pseudotumor cerebri") are elevated intracranial pressure, normal neurologic findings except for papilledema and occasional CN VI palsy, absence of a space-occupying lesion or ventricular enlargement on CT, and normal CSF composition.24

The differential diagnosis of diplopia includes processes that affect the muscles (for example, thyroid disease or other myopathies), the neuromuscular junction (myasthenia gravis, botulism), or CN function. The CNs may be affected by extrinsic compression (for example, structural lesions) or by intrinsic pathologies (such as ischemia).

CN VI is the longest intracranial CN, and an isolated CN VI palsy is often caused by head trauma. It is rarely caused by processes that affect the neuromuscular junction or the muscles, since these processes generally have more diffuse effects. Approximately 30% of patients with IIH have a CN VI palsy, which in those cases is labeled a "false lateralizing sign."25 n

References:

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