Chapter 15 - Evaluation of the Ataxic Patient

Introduction

Ataxia is defined as a difficulty of gait. It is a very common neurologic complaint, particularly in an elderly population and is often multifactorial. In general terms, ataxia can result from damage to the sensory systems that provide feedback for normal balance, or problems with the several motor systems that are needed to respond to the constantly changing environment while walking.

The sensory systems that are important to gait include the visual system, the vestibular system and the conscious proprioceptive system from the lower limbs (especially the feet). When one of these systems is not functioning (such as when the eyes are closed) one becomes more dependent on the others. There are also certain times when one becomes more dependent on the sensory systems (such as the dependency on sensations from the feet when the ground is rough or irregular). Also, when a sensory system is functioning abnormally (such as when the patient has vertigo from abnormal vestibular function) it becomes difficult to maintain normal balance.

The motor systems that are necessary for normal gait include those responsible for strength (upper and lower motor neurons), coordination (the cerebellum) and muscle tone and postures (the extrapyramidal system). Also, there are cortical elements necessary for gait that will be discussed below.

Finally, there are patients who cannot stand due to other factors, such as orthostatic hypotension, that occur when upright.

History

There are several questions that can aid in focusing the evaluation.

How long has it been present and did it begin all of sudden? These are common questions in neurology and help distinguish chronic and slowly progressive problems (such as degenerative diseases like Parkinson disease) from acute problems (like stroke).

When does it occur? It is important to note the circumstances under which the patient's gait is notably abnormal. For example, if walking on irregular surfaces or in the dark markedly worsens the patient’s gait, sensory ataxia should be a major consideration.

Are there any coexisting symptoms? These may include vertigo, weakness, stiffness or slowness of movement, abnormal movements, cognitive difficulties or significant changes in behavior. These can be clues to vestibular, cerebellar, pyramidal, extrapyramidal or frontal lobe disorders. Feelings of presyncope may require evaluation of factors potentially affecting blood flow to the brain (chapter 27).

What has been the functional ramifications of the gait disturbance? For example, has the patient fallen and, if so, in what situations? What has the patient or family done to prevent falls (i.e., restrict movements, etc).

Is the gait disturbance completely explainable by pain (such as a limp), or by compensation for weakness of a single muscle group? If it is due to weakness, evaluation of this symptom (chapter 12) will be the most important factor.

Is the gait disturbance real and have others noticed it? This is important because ataxia can be hysterical in nature. At times this can be recognized by the severity of the gait disturbance (which is often exaggerated and bizarre) and the relative paucity of injuries due to falls, etc. These patients often “catch themselves” in ways that would suggest higher levels of motor performance than their poor gait would indicate. Astasia-abasia is a term that has been applied to the condition in which the patient lurches wildly and only falls when there is someone or something to break the fall. The key to recognizing this is to realize that the ability to catch themselves exceeds that which would be expected of a patient with such sever gait disturbance.

Examination

The examination of the patient with ataxia is focused on evaluating those systems necessary to maintain the upright posture. During portions of the neurologic examination, screening tests of strength, muscle tone, coordination, the vestibular system, the conscious proprioceptive system, and cortical function (especially the frontal lobes) must be included. Of course, it is most critical to watch the patient walk. Patients with ataxia tend to compensate by broadening their base of support (normally, the medial side of each foot strikes along a straight line when walking). Examining the patients posture when standing with the feet together is important. If they are steady with the eyes open but not with the eyes closed (Romberg sign), loss of proprioception in the feet should be suspected.

Conscious proprioceptive sensory system. One of the most common causes of ataxia is loss of proprioception in the feet. This can be tested by examining vibratory and joint position sense at the great toe. These patients have worsened symptoms when walking on irregular surfaces or when their vision is obscured and they usually broaden their base of support. They also have trouble standing with their eyes closed (Romberg sign) and the ataxia markedly improves simply by touching a stationary object or running the hand along the wall (in a sense, replacing the lost sensitivity of the feet). Although elderly patients often lose some sensitivity at the toes, the various causes of polyneuropathy or dorsal column damage should be considered if the sensory loss is out of proportion for age. It is noteworthy that these patients improve dramatically when walking with a cane.

Vestibular system. Vestibular problems are usually easy to recognize by history and exam. The patient is likely to be vertiginous and will usually show nystagmus that is at least in proportion to their vertigo. They will tend to veer to one side when they try to walk a straight line. The evaluation of such patients is conducted according to the protocol for evaluating the dizzy patient found in chapter 14.

Cerebellar system. The ataxia of cerebellar disease tends to produce a broad-based, lurching, reeling or drunken kind of gait. The ataxia often involves the trunk with titubation. The symptoms of imbalance are usually manifest while trying to stand with the feet together even with the eyes open. Eye closure usually only slightly worsens the imbalance. Most often, patients have other signs of cerebellar disease, such as speech disturbance or in coordination of the limbs. The broad differential diagnosis of cerebellar disease can be found in this table.

Strength. It is important to consider whether the patient has adequate strength to stay upright. If weakness is an issue, do they have signs of upper motor neuron damage (hyperactive reflexes, spasticity or Babinski sign) or lower motor neuron damage (diminished reflexes, atrophy or, possibly, fasciculations). Do they have a weakness that suggests myopathy (proximal – hip and shoulder girdle) or generalized neuropathy (distil). If the patient is weak, it is essential to assess whether their degree of gait difficulty is fully explained by the weakness.

There are several very specific gait disturbances associated with weakness. For example, weakness of the hip girdle muscles causes the pelvis to shift toward the side of weakness when walking. When the hip girdle weakness is bilateral the gait is described as "waddling." A foot-drop will cause the patient lift that leg higher, and the gait disturbance is called a “steppage” gait. Weakness of the quadriceps muscles will cause the patient to swing the affected leg forward and lock the knee at the time of heel-strike in order to prevent the leg from collapsing.

Extrapyramidal system. Extrapyramidal disorders, such as Parkinson disease, commonly affect gait. In the case of Parkinson disease, patients tend to have rigidity with slowed movements. They have slowed or delayed postural corrections when they are bumped off balance. Curiously, they tend to walk with a narrow base of support, which is counterintuitive. Most of the other causes of extrapyramidal gait disturbance result in some broadening of the base of support. Some of these other conditions produce this tone is more limitations and vertical gaze. Additionally, there may be other abnormal movements at rest. He should be sought during the exam.

Frontal lobes. Damage to the frontal lobes, often produces a curious kind of gait disturbance called “apraxia” of gait. The patient tends to slide their foot along the floor instead of lifting and placing normally. This has been called a “glue-footed" or "magnetic" gait, and the patient may be retropulsive if this is severe. Primitive reflexes such as grasp, snout, palmomental and glabellar responses are likely to be disinhibited, and the patients personality or cognitive function are often impaired. When severe, these kinds of frontal lobe conditions may result in incontinence, which typically occurs without warning. Conditions such as frontal lobe strokes, tumors or normal pressure hydrocephalus should be considered as possible causes, although generalized dementing illnesses can also involve frontal lobes. In patients with generalized dementia, such as Alzheimer disease, gait disturbance is usually found in the latter stages.

Summary

In summary, the evaluation of any ataxia requires assessment of those systems that are necessary to maintain the upright posture. In the elderly, the problem may well be multifactorial. Nonetheless, each of the problems that may be contributing to the gait disturbance require investigation in order to determine whether further deterioration can be prevented. Remediation of the gait disturbance may be relatively simple (such as the use of cane in patients with sensory ataxia or braces in patients with focal weakness). Additionally, specific treatment of disorders such as Parkinson disease may result in dramatic improvement in gait. It is important to be systematic and aggressive in the evaluation and management of gait disturbance since this symptom is not only terribly limiting for patients, but also because falls represent a major health risk, especially in the elderly.

Questions

Define the following terms:

conscious proprioception, agnosia (sterioagnosia), graphesthesia, dermatome, sclerotome, myotome, radiculopathy, myelopathy, anesthesia/hypoesthesia, hyperpathia, allodynia, hyperesthesia, dysesthesia, paresthesia, polyneuropathy, subjective.

Conscious proprioception is the ability to tell where a body part is in space. It is largely based on joint position sense.

Agnosia (sterioagnosia) ia the inability to recognize what a sensation is despite relatively normal perception of the sensation. When it is tactile it is termed sterioagnosia (or asteriognosis). It would be the inability to determine the denomination of a coin despite normal ability to perceive it, for example.

Graphesthesia is the ability to identify letters or figures traced on the skin (without looking).

Dermatome is the area of skin supplied by a nerve root.

Sclerotome is the area of bone and joints supplied by a single nerve root.

Myotome is the muscles supplied by a single nerve root.

Radiculopathy this is damage to a nerve root (radiculitis is irritation).

Myelopathy is damage to the spinal cord from any cause.

Anesthesia/hypoesthesia is loss (or decrease) in sensation.

Hyperpathia is the exaggerated perception of normally painful stimuli.

Allodynia is the perception of normally innocuous stimuli as being painful.

Hyperesthesia is excessive sensitivity to any modality.

Dysesthesia is the perception of the pain when no stimulus is present.

Paresthesia is the abnormal perception of a sensation in the absence of any stimulus.

Polyneuropathy is generalized damage to peripheral nerves. This is usually due to a systemic cause.

The sensory exam is by definition subjective, that is, relies on the patients report.

15-1. What systems are important to normal, safe ambulation?

15-1. There are sensory and motor systems that are important. On the sensory side, vision, somatic sensation (conscious proprioception) from the feet and the vestibular system are important. On the motor side, adequate strength (upper and lower motor neurons), cerebellar systems and extrapyramidal systems are employed in ambulation. The frontal lobes of the cerebral cortex are also involved in normal gait.

15-2. What gait disturbance is seen with pain?

15-2. Patients limp in order to protect an injured area.

15-3. What kind of gait disturbance would you expect to see in the patient with dysfunction of conscious proprioception (either a large fiber polyneuropathy or dorsal column damage)?

15-3. They experience disequilibrium. The patient has a wide based gait and they often look at their feet while walking. They have many more problems walking in the dark and on irregular ground and usually have a very noticeable Romberg sign. Their imbalance improves dramatically by touching a stationary object.

15-4. What symptoms would suggest vestibular abnormality as the cause of ataxia?

15-4. Patients with vestibular problems are usually vertiginous and nystagmus may be seen on examination. They will usually tend to veer or deviate toward one side when walking, especially if their eyes are closed or if they are asked to walk tandem.

15-5. What symptoms would suggest cerebellar abnormality as the cause of ataxia?

15-5. Patients with cerebellar ataxia often have trunkal ataxia and other signs of cerebellar disease, such as speech disturbance or limb incoordination. Their gait tends to be a reeling or drunken type of gait and they have trouble standing with the feet together regardless of whether their eyes are open or closed.

15-6. What role does strength play in gait?

15-6. Of course, strength is necessary to be able to stand and walk. There are some specific gaits: the waddling gait of hip girdle weakness; the steppage gait of foot-drop; the swinging gait of quadriceps weakness; and the circumducting or scissors gait of upper motor neuron weakness. An important question is whether the degree of their ataxia explained by their weakness. If weakness is a significant problem, then the investigation of weakness should proceed as in chapter 12.

15-7. What symptoms would suggest extrapyramidal abnormality as the cause of ataxia?

15-7. The most common extrapyramidal disorder is Parkinson disease, although there are a large number of other, rare conditions that cause “parkinsonism.” Most of these conditions produce a type of increased tone called rigidity, and postural reactions are often slowed or delayed. Postural corrections can be tested by standing behind the patient and then attempting to pull them over suddenly (of course, you must be prepared to catch them). Other clues to abnormal extrapyramidal function include abnormal movements at rest and slowed eye movements (some conditions prevent voluntary vertical eye movements). Some involuntary movements, such as myoclonus, chorea or asterixis can introduce abnormalities in gait.

15-8. What symptoms would suggest frontal lobe disease or degeneration as the cause of ataxia?

15-8. The classic gait of frontal lobe disease is “apraxia.” This consists of a gait in which the person slides their feet along the floor (“magnetic” or “glue-footed”). They are likely to have signs of personality change or cognitive change (the latter especially if the frontal lobe dysfunction is part of a more generalized cortical dysfunction). Frontal lobe dysfunction often leads to incontinence of a curious type where there is little or no warning.

15-9. What symptoms would suggest frontal lobe disease or degeneration as the cause of ataxia?

15-9. The classic gait of frontal lobe disease is “apraxia.” This consists of a gait in which the person slides their feet along the floor (“magnetic” or “glue-footed”). They are likely to have signs of personality change or cognitive change (the latter especially if the frontal lobe dysfunction is part of a more generalized cortical dysfunction). Frontal lobe dysfunction often leads to incontinence of a curious type where there is little or no warning.

15-10. Is this gait disturbance real?

15-10. This is an important question since “inability to walk” can be hysterical. There are several important questions to ask when examining the patient. Is the gait disturbance consistent with known patterns of difficulty? Have others noticed it? Does it affect functioning in the way and to the degree that you would expect given the complaints? Has it resulted in falls? Does the patient manifest astasia-abasia (severe lurching, but catching themselves prior to injury) that would suggest substantially higher function than they are manifesting?

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