What Is Normal Neurological Aging?

The diagnosis of neurological disease in the older adult requires recognition not only of abnormal signs and symptoms but also an understanding of what changes are expected as part of the normal aging process. To distinguish neurological dysfunction related to disease from the neurological changes associated with normal aging, the clinician must conduct a comprehensive mental status and neurological examination. When establishing a neurological diagnosis, the clinical history (i.e., history of the present illness, past medical history, social habits, occupational experience, family illness, and disorders) assists the clinician in generating a differential diagnosis that can be further explored and refined by pertinent observations documented on the mental status and neurological examinations. The mental status assessment should evaluate cognition, emotion, and behavior. Because cognitive and affective disorders occur commonly in older adults, historical information should be obtained not only from the patient but a reliable informant such as the spouse, adult child, or caregiver. The neurological examination should be performed on all older adults regardless of the chief complaint as up to 60% of older patients have either a primary or secondary neurological sign or symptom. A complete mental status and neurological examination provides the necessary data to develop reasonable diagnostic hypotheses and drive the necessary laboratory, imaging, or specialized assessments to care for the patient.

Age-Related Changes in the Neurological Examination

Before discussion of the individual components of the examination, it would be useful to discuss changes that are expected as part of the aging process (Table 12-1). Normal age-related changes are due to progressive and irreversible changes associated with tissue senescence and the inability of nervous system to repair and regenerate secondary to the ravages of time. The frequency and qualitative characteristics of these changes vary from individual to individual but are present in many older adults.

Cognitive Changes

There continues to be a debate as the extent of cognitive changes associated with aging due largely to differences between cross-sectional and longitudinal study designs. When comparing older adults to young adults on similar cognitive tasks such as the Wechsler Adult Intelligence Scale, older adults generally score lower on both performance and verbal subtests. However, when differences in performance are considered in light of motor slowing and educational attainment, these changes are less apparent. Longitudinal evaluation of older adults has generally demonstrated little change in verbal intelligence with aging while performance is influenced significantly by motor and processing speed. Forgetfulness therefore is not part of normal aging. While it may take longer to process new information and retrieve well-learned information, new learning and memory formation occurs in older adults. This is one reason why delayed recall of word lists is effective in discriminating older adults with cognitive impairment from those without impairment.

Changes in Cranial Nerve Function

Visual and hearing changes are common in the older adult. Visual acuity declines because of a number of ophthalmologic (cataracts, glaucoma) and neurological (macular degeneration) causes. Pupillary size is typically smaller with age and pupils are less reactive to light and accommodation, forcing many older adults to use glasses for reading. There is also a restriction in eye movement in upward gaze. Also associated with aging is a decline in speech discrimination due to presbycusis, a progressive elevation in the frequency threshold for hearing. There are also age-related degenerative changes in inner ear including loss of hair cells, atrophy of stria vascularis, and thickening of the basilar membrane.

Changes in Motor Function

There is a progressive decline in muscle bulk and strength associated with aging. Most of the muscle loss is found in the intrinsic muscles of the hands and feet, and around the shoulder. There is a weakening of the abdominal muscles, which may accentuate spinal lordosis and contribute to low back pain. Muscle loss is associated with denervation on electrophysiological studies and with type II atrophy on muscle biopsy. In addition to loss of strength and muscle bulk, changes in the speed and coordination of movement increases with advancing age. The changes may interfere with activities of daily living (dressing, putting away the dishes, getting out of a chair) and recreation activities (golfing, shuffleboard). On examination, these changes may manifest as mild bradykinesia and dysmetria on finger-nose-finger and heel-shin tests.

Changes in Sensory Function

By far the most common change will be the loss of vibration perception in the lower extremities and to a lesser extent position-sense may be affected as well. As vibration sensation becomes impaired in lower extremities, there is an ascending pattern, from toe to ankle and knee. Pain and temperature sensation is also diminished in the older adult, but in the absence of a pathological cause, usually does not elicit much symptomatology. The mild impairment in position sense often manifests as a mild swaying during the Romberg test.

Changes in Gait and Station

Changes in gait and station in old age may be attributed in part to decreased muscle strength, weakening of abdominal muscles, arthritis, and degenerative joint disease, diminished vibration and position sense, impairment in motor speed and coordination. These changes make it more difficult for older adults to tandem, heel, or toe walk for extended periods of time. Despite this, most older adults have adequate postural righting reflexes and are not likely to spontaneously fall (distinct from what is seen in Parkinson’s disease).

Changes in Deep Tendon Reflexes

The most common age-associated change is the depression or loss of the Achilles tendon reflex. Other reflexes usually remain present but are diminished in response. An extensor plantar response (Babinski sign) is not a normal age-related change but instead is always associated with some underlying pathology in the upper motor neuron.

There is no substitution for a carefully elicited history detailing the onset, duration, quality, and location of symptoms. The history helps the clinician develop a differential diagnosis and focus on the neurological examination. The history will also guide the formulation of diagnostic evaluations and develop a treatment plan. In addition, a compassionate clinician will be able to build a trusting relationship with the patient that will enhance patient adherence to medical recommendations. As a general comment, to avoid bias, it is often useful to gather historical facts de novo and not read other records or review laboratory studies such as imaging before taking the history and performing the physical examination. In this section, we discuss two aspects of neurologic history taking—from the patient and, when available, from an informant.

Neurological History from the Patient

An accurate history requires that absolute attention is paid to detail, both verbal (what the patient is saying) and nonverbal (what the patient is doing). This is critical to match the chief complaint with the patient’s body language. For example, someone complaining about severe low back pain but appears to be sitting comfortably in the chair may raise suspicion. Likewise, the older adult who offers no complaints but is noted to have a rest-tremor should prompt more detailed questioning. One of the most important attributes of a skilled clinician is the ability to be a good listener and to focus in on critical historical points. The most effective historians gather information by a combination of open-ended and structured questions. After asking the patient why they are in office and offer a chance to express concerns or worries in their own words, specific topics can be addressed by focused questioning.

Another important aspect of the history is to elicit qualitative and quantitative aspects of the chief complaint. It is not enough to elicit a history of a “headache” or “pain.” What are the characteristics of the complaint, when did it start, what makes it better, what makes it worse? Has this happened before, and if so, did it present in the same fashion? Use simple scales to quantify the extent of the complaint by asking “On a scale of 1 to 10, with 10 being the worse (symptom)…” These qualities can help focus a differential diagnosis and helps to build trust with the patient.

Neurological History from an Informant

In many instances, gathering information from a third party will be invaluable in determining the onset, duration, and extent of the neurologic problem. In cases where there are problems with cognition or alertness, this may be the only reliable way to gather information. Again, using both open-ended and structured questions will often provide the clinician with important information about the chief complaint and assist in the development of a differential diagnosis.

The elements of a comprehensive mental status examination include observational, cognitive, functional, and neuropsychiatric assessments. Although each of these elements is presented separately, they are interrelated and collectively characterize the neurobehavioral function of the patient. The initial contact with the patient affords the opportunity to assess whether a cognitive, attention, or language disorder is present. Questioning of an informant may bring to light changes in cognition, function, and behavior that the patient either is not aware of or denies.

Observational Assessment

Observation of a patient’s level of arousal or alertness, appearance, emotion, behavior, movements, and speech provides insight into their mental status.

Level of Consciousness

An accurate assessment of a patient’s mental status and neurologic function must first document the patient’s alertness or level of arousal. Altered levels of consciousness can directly impact the patient’s cognitive performance on mental status testing and influence the examiner’s interpretation of the test results and maybe indicative of a medical or neurologic condition requiring immediate medical intervention (e.g., cardiopulmonary intervention, neurosurgical evaluation).

Abnormal patterns of arousal include hypoaroused or hyperaroused states. Decreasing levels of arousal include lethargy, obtundation, stupor, and coma. The lethargic patient is drowsy or fatigued and falls asleep if not stimulated; however while being interviewed, the patient will usually be able to attend to questioning. Obtundation refers to a state of moderately reduced alertness with diminished ability to consistently engage the environment. Even in the presence of the examiner, if not stimulated, the obtunded patient will drift off. The stuporous patient requires vigorous stimulation to be aroused. Responses are usually limited to simple “yes/no” responses or may consist of groans and grimaces. Coma, which represents the end of the continuum of hypoarousal states, is a state of unresponsiveness to the external environment. In the elderly, hypoarousal states can be associated with systemic infection, cardiac or pulmonary insufficiencies, meningoencephalitis, increased intracranial pressure, toxic-metabolic insults, traumatic brain injury, seizures, or cerebrovascular disease. Coma requires either bilateral hemispheric dysfunction or brainstem dysfunction. Another important consideration is the role of polypharmacy. Drug interactions are more common in the older adult and can significantly impair consciousness.

Hyperarousal states, on the other hand, are characterized by anxiety, autonomic hyperactivity (tachycardia, tachypnea, hyperthermia), agitation or aggression, tremor, seizures, or exaggerated startle response. In the elderly, hyperarousal states are most often encountered in toxic-metabolic disorders including withdrawal from alcohol, opiates, or sedative-hypnotic agents. Other causes include tumors (both primary and metastatic), viral encephalitis (particularly herpes simplex), cerebrovascular, and hypoxemia. Some patients may experience fluctuating periods of both hypo- and hyperarousal.

Appearance

Assessment of a patient’s physical appearance should acknowledge body size and type, apparent age, posture, facial expressions, eye contact, hygiene, dress, and general activity level. A disheveled appearance may indicate dementia, delirium, frontal lobe dysfunction, or schizophrenia. Wearing excessive makeup or flamboyant grooming or attire in an old individual should raise the suspicion of a manic episode or frontal lobe dysfunction. Patients with unilateral neglect may fail to dress, groom, or bathe one side of their body. Patients with Parkinson’s disease may display a flexed posture, whereas patients with progressive supranuclear palsy have an extended, rigid posture. The overall appearance of an individual should also provide information regarding their general health status. The cachectic patient may harbor a systemic illness (e.g., cancer), or have anorexia or depression.

Emotional State and Affect

Affect describes the mental representation of external reality and the patient’s internal feelings about external reality, while emotional state describes the objective display of emotion through facial grimaces, vocal tone, and body movements, and the subjective component of how the patient reports what he or she feels internally: “I feel sad, happy, apprehensive, cynical.”

Depression is the most frequent mood disturbance in the older adult and occurs in a variety of neurologic disorders (Table 12-2). Euphoria or full-blown mania occurs less often than depression in the course of neurological illness. Euphoria is most common with frontal lobe dysfunction (trauma, frontotemporal degenerations, infections) and with secondary mania. Anxiety occurs in a variety of neuropsychiatric conditions including anxiety disorders, metabolic encephalopathies (e.g., hyperthyroidism, anoxia), toxic disorders (e.g., lidocaine toxicity), and degenerative diseases (e.g., Alzheimer’s disease, Parkinson’s disease). Objective and subjective emotional components may be incongruent in certain psychiatric disorders (e.g., schizophrenia and schizotypal personality disorder), and in neurologic conditions such as pseudobulbar palsy.

The range and intensity of the observable component of emotion should be noted. Constriction or flatness is observed in apathetic states; for example, in the context of negative symptoms of schizophrenia, severe melancholic depression, or in demented patients with apathy. Increased intensity, on the other hand, is seen in mood disorders such as bipolar illness, and in personality disorders such as borderline personality.

Lability is a disorder of emotional regulation. Patients with marked lability are irritable and shift rapidly among anger, depression, and euphoria. The emotional outbursts are usually short-lived. Labile mood is seen in mood disorders such as bipolar illness and in certain personality disorders such as borderline personality. It also may occur in frontotemporal dementia and pseudobulbar palsy.

Behavior

Behavioral observations can reveal important information regarding the mental status and neurological function of the patient. A variety of personality alterations can be encountered with focal brain lesions. Orbitofrontal dysfunction maybe characterized by impulsiveness or undue familiarity with the examiner, lack of judgment or lack of social anxiety, and antisocial behavior. Individuals with dorsolateral frontal lobe dysfunction may be inattentive and distractible. Apathy (lack of motivation, energy, emotional reciprocity, social isolation) may be caused by medial frontal dysfunction. Dementias are associated with increased rigidity of though, egocentricity, diminished emotional responsiveness, and impaired emotional control.

Movement

Observation of patient’s movements may provide evidence of parkinsonism, chorea, myoclonus, or tics (Table 12-3). Psychomotor retardation (i.e., slowed central processing and movement) may be indicative of vascular dementia, subcortical neurological disorders, parkinsonism, medial frontal syndromes, or depression. Psychomotor agitation may be indicative or a metabolic disorder, choreoathetosis, seizure disorder, mania, or anxiety.

Speech and Communication

Observation of spontaneous speech is the first step in formal language testing and can be assessed during history taking as well as in the course of the mental status examination. The examiner first observes spontaneity of speech as well as the timber, pitch, and modulation of voice. Mutism maybe encountered in several neurological conditions such as akinetic mutism, vegetative state, locked-in syndrome, catatonic unresponsiveness, or large left hemispheric lesions. Akinetic mutism is characterized by absent speech in the setting of alert-appearing immobility. The patient’s eyes are open, and the individual may follow environmental events. The patient exhibits regular sleep–wake cycles but may be completely inert or display brief movements or postural adjustments spontaneously or in response to vigorous stimulation. Akinetic mutism may be seen with large frontal lobe injuries, bilateral cingulate gyrus damage, or midbrain pathology. Akinetic mutism should be distinguished from a vegetative state where the patient exhibits sleep–wake cycles with open eyes. A vegetative state can occur after severe brain injury. Locked-in syndrome occurs with bilateral pontine lesions, rendering the patient mute and paralyzed. Intellectual function, however, is not impaired and the patients can communicate by eye movements or eye blinks.

Spontaneous speech is characterized by its rate, rhythm, volume, response latency, and inflection. Accelerated speech may be encountered in mania, disinhibited orbitofrontal syndromes, or festinating parkinsonian conditions, whereas a reduced rate of speech output can occur as a component of psychomotor retardation. Response latencies may be prolonged or the patient may impulsively interrupt the examiner, anticipating the question. Perturbed speech prosody (loss of melody or inflection) can be encountered in brain disorders affecting the right hemisphere or the basal ganglia. Empty speech with hesitations or circumlocutions can be exhibited in patients with word-finding difficulties. Word-finding impairment may occur in aphasias, metabolic encephalopathies, physical exhaustion, sleep deprivation, anxiety, depression, or dorsolateral frontal lobe damage in the absence of an anomia.

Aphasia is characterized by impairment in oral and/or written communication. Deficits will vary depending on the location and extent of anatomic involvement. Aphasias are generally characterized as nonfluent or fluent (Table 12-4). Nonfluent aphasias are characterized by a paucity of speech, often with a hesitant quality. There is impairment in word searching and writing. The patient may appear frustrated or depressed because of awareness of the language deficit and the inability to communicate with family and health care providers. Fluent aphasias are characterized by empty speech. Word production is normal or maybe increased but there is a lack of comprehension about what words mean, often associated with impairment in reading ability. The patient often displays little insight to the language deficit and instead may become agitated because others are not following the conversation.

Cognitive Assessment

The assessment of cognitive function should be conducted methodically and should assess comprehensively the major domains of neuropsychological function (attention, memory, language, visuospatial skills, executive ability). The patient’s age, handedness, educational level, and sociocultural background may all influence cognitive function and should be determined prior to initiating or interpreting the evaluation.

Attention

Two tests are useful in assessing attention: digit span forward and continuous performance tests. In the digit span forward test, the patient is asked to repeat increasingly long series of numbers (e.g. 1, 3–7, 4–6-3, 5–1-9–2, etc). The examiner says the numbers at a rate of one per second. A normal forward digit span is seven digits; fewer than five is abnormal. Concentration is evaluated by a continuous performance test. An example would be to say the months of the year in reverse order, starting with the last month of the year (December). Distractible patients tend to lose track and skip one or two months. Serial subtraction can also be used to test concentration but heavily dependent on educational attainment and mathematical abilities. Confusional states such as delirium are characterized by impaired attention.

Memory

Learning, recall, recognition, and memory for remote information are assessed in the course of mental status examination. Asking the patient to remember three words and then asking him or her to recall the words 3 minutes later can help assess learning, recall, and recognition. However, the shorter the list, the more easy it is to remember, particularly in high-functioning individuals. When told to remember items, patients will often remember the first two items heard (known as “primacy”) and the last two items heard (known as “recency”), therefore longer lists of 10 words may be preferable. After a delay, recall of less than five words is considered abnormal. Patients having difficulty with recall may be given clues (e.g., the category of items to which the word belongs or a list of words containing the target) to distinguish between storage and retrieval deficits. Prompting and clues will not aid patients with storage deficits (e.g., amnesia); patients with intact storage but poor recall (e.g. retrieval-deficit syndrome) may be aided by clues. Amnestic deficits are thought to be causes by lesions in the hippocampal–thalamic circuit while retrieval deficits are likely due to lesions of frontal–basal ganglia circuitry.

Information is gathered on the patient’s remote memory function while taking a history of the patient’s illness, inquiring about the patient’s life events (marriage, births of children, etc.), and asking about important historical events. An informant may also be helpful here to verify these events. The temporal profile of remote memory may be diagnostically important. Amnestic syndromes such as dementias usually feature normal, nonmemory cognitive functions, a period of retrograde amnesia following the onset of the disorder, variable periods of anterograde amnesia, and intact remote memory beyond the period of the retrograde amnesia. Psychogenic memory loss may include variable patterns of amnesia particularly in long-term events (e.g., not recall birth of children, not recall being married).

Language

Language assessment entails the evaluation of all aspects of communication including spontaneous speech, comprehension, repetition, naming, reading, and writing. Aphasic disturbances are characterized as fluent or nonfluent. Fluent aphasias are characterized by normal or excessive amounts of speech, preserved phrase length, intact speech melody, usually in combination with a paucity of information. Phonemic paraphasias (substitution of one phoneme for another); semantic paraphasias (the replacement of one word with another); or neologistic paraphasias (the construction of new words) may occur. Wernicke, transcortical sensory, conduction, and anomic aphasias are fluent aphasic syndromes.

Nonfluent aphasias feature reduced verbal output, short or one-word replies, agrammatism, poor speech initiation, reduced speech prosody, and dysarthria. There are few paraphasias. Broca, transcortical motor, global, and mixed transcortical aphasias are nonfluent aphasic disorders. Interestingly, nonfluent aphasic patients may have preserved abilities to curse fluently and sing well-learned songs (i.e., Happy Birthday) with few errors.

Primary progressive aphasia is a disorder seen in patients with asymmetric frontotemporal degeneration that involves dominant hemisphere. Progressive nonfluent aphasia involves primarily unilateral left frontal, left frontoparietal, or left frontotemporal degeneration and is characterized by agrammatism, paraphasias, and anomia. Bilateral temporal lobe atrophy and hypoperfusion with more pronounced involvement of the left anterior temporal lobe may cause semantic dementia that is characterized by progressive loss of knowledge about objects, people, facts, and words, often accompanied by visual agnosia (inability to name or recognize objects presented visually).

Language comprehension is tested by asking the patient to follow increasingly complex linguistic constructions. The easiest commands are one-step orders such as “stand up” and “turn around,” “open your mouth,” and “stick out your tongue.” Asking the patient to point to room objects or body parts is the next level of comprehension difficulty. Finally, more complex questions such as “If a lion is killed by a tiger, which animal is dead?” are asked. Impaired comprehension usually implies dysfunction of parietotemporal regions of the left hemisphere. Comprehension is abnormal in most fluent and global aphasic syndrome but may be preserved in nonfluent syndromes. In the elderly, it is important to establish that hearing is intact before testing comprehension. Failure to comprehend commands may reflect the inability to hear as opposed to impaired comprehension.