Ataxia is defined as a syndrome characterized by lack of coordination of movements and posture secondary to a variety of reasons:
Sensory ataxia: Proprioceptive loss causes the brain to be unaware of the position of limbs and trunk. Thus, there is incoordination of movements because of incomplete feedback. For example, the major mechanism by which we are able to maintain our balance while walking on uneven ground comes from the proprioceptive feedback from muscles and tendons around the ankle. Loss of ankle proprioception results in problems with balance.
Optic ataxia: Caused by damage to the parietal lobes, it is characterized by a dysfunction of reaching movements under visual guidance (see chapter on Dementias).
Cerebellar ataxia: The cerebellum is involved in coordination of movement of different muscle groups. Problems with the cerebellum cause the various manifestations of cerebellar ataxia.
Vestibular ataxia: Loss of balance and coordination in the setting of vestibular system dysfunction or its connections. Patients with chronic bilateral loss of vestibular function report a sense of unsteadiness, dizziness, vertigo, post-movement gaze variability, and oscillopsia.
CASE 30-1
You are the neuro-hospitalist on call and get a page from the Urgent Care Clinic to consult on a patient with problems with gait and balance. This is the second time he presented to Urgent Care with similar complaints over the past weeks. During the last visit, the physician had suspected cervical spine stenosis and obtained an MRI of the brain and cervical spine. He had also referred the patient to ENT for assessment of vestibular function who had thought that a vestibular disorder did not explain the symptoms fully. The clinic attending says she thinks the patient has ataxia.
From the history, we may elicit the common symptoms of cerebellar ataxia. The key features in disorders presenting with cerebellar ataxia are the presence of poor balance with falls, imprecise hand coordination, postural or kinetic tremors of the extremities or trunk, dysarthria, dysphagia, vertigo, and diplopia.
Lack of balance. Patients complain of not being able to walk in a straight line and bumping into walls. The patient often walks in a zigzag and reports that it feels like ambulating on a boat. The companions may note the patient walks like a drunk person.
Incoordination. The patient may complain of clumsiness and problems with skilled tasks. They may drop objects or have problem with reaching for items.
Tremor. Two kinds of tremors are seen in patients with cerebellar ataxia. They complain of hand shaking when reaching for things or trying to do something. Some complain of head shaking especially while sitting. Cerebellar tremors are worse at the end of the movement with variable amplitude and low frequency around 3–5 Hz.
Dysarthria: Dysarthria is a problem with articulation of speech. There are several kinds of dysarthrias:
Bulbar dysarthria: This is the result of muscle, neuromuscular junction, or lower motor neuron disease. The patient sounds nasal, and there is particular problem with enunciating consonants.
Pseudobulbar dysarthria: This is due to spasticity because of an upper motor neuron process. The patient sounds like they are squeezing the words through their mouth. Patients with cerebral palsy have this kind of dysarthria.
Cerebellar dysarthria: This is seen in the context of cerebellar ataxia. There is a problem with regulating the pitch and volume of syllables. The patient sounds drunk.
Dysphagia: Problems with coordination of muscles of deglutition can impair swallowing.
Visual symptoms: Blurring of image especially of moving objects may be reported. Patients with cerebellar dysfunction commonly develop oculomotor abnormalities including nystagmus, slow saccades, and abnormal smooth pursuit.
CASE 30-1 (continued)
You enter the consultation room and see a slightly built man. His wife accompanies him. He is 60 years of age and has been having gait problems for 5 years. He first noticed problems during exercise with gait difficulties if tired, but by now, he needs to use a wheelchair and has had a number of falls. He relates he has had a history of weight loss in the last few months and says his legs are now like “chicken legs.”
There are four factors that help narrow the differential diagnoses:
Asymmetry: Asymmetrical presentation can significantly narrow the differential diagnosis in ataxia. As a rule of thumb, asymmetrical presentation is due to a pathology that may be visible on neuroimaging. These include space-occupying lesions such as abscesses and tumors; tissue damage and gliosis as in multiple sclerosis or stroke; and anatomical variants such as Dandy-Walker and Chiari malformations.
Acuity of presentation: Most of the etiologies for cerebellar ataxia include toxic effects, infections, autoimmune conditions, metabolic, and hereditary diseases. The latter is almost always chronic. Based on the acuity of presentation, we can narrow this large field down for more targeted testing:
Acute:
Cerebellar toxins: alcohol, lithium, phenytoin, amiodarone
Infections: viral infections, in particular Epstein-Barr virus (EBV) and Varicella Zoster virus (VZV) seen more commonly in children
Autoimmune: postviral or postvaccination
Metabolic: Wernicke encephalopathy
Subacute:
Toxic exposures: heavy metals such as mercury and thallium, antimetabolite chemotherapies (Ara-C and 5-FU), and volatile organic materials such as solvents, glue, and toluene
Infections: Lyme neuroborreliosis
Autoimmune: paraneoplastic, Bickerstaff encephalitis
Metabolic: copper, vitamin B1, B12, and vitamin E deficiencies
Chronic:
Toxic: phenytoin, amiodarone, and alcohol
Infectious: tertiary syphilis (but mostly sensory ataxia)
Autoimmune: anti-GAD 65 ataxia, and gluten ataxia
Metabolic: hypothyroidism (mild)
Hereditary: autosomal dominant, autosomal recessive, X-linked, and mitochondrial
Age of onset:
Infancy and childhood: congenital causes including intrauterine injury, Joubert syndrome, and viral disease
Adolescence: Friedreich’s ataxia and other autosomal recessive conditions. Most patients with autosomal dominant conditions develop symptoms at <20 years of age regardless of etiology
Middle aged: autosomal dominant conditions, acquired ataxia, and sporadic idiopathic ataxias
Old age: autosomal dominant ataxias (spinocerebellar ataxia (SCA)6), acquired ataxia, and sporadic idiopathic ataxias
Other associated symptoms
Signs and symptoms of alcohol abuse (alcoholic ataxia)
Autonomic failure: multisystem atrophy cerebellar type—MSA-C. This used to be called olivopontocerebellar degeneration, but such term is not specific and should not be used in this context. In superficial central nervous system (CNS) hemosiderosis, linear hypodensities are seen around the cerebellum and brainstem (Figure 30-1).
Known or previous malignant disease, fevers, or weight loss: paraneoplastic syndromes
Rapid onset: infections, paraneoplastic syndromes, and steroid-responsive autoimmune encephalopathy (Hashimoto encephalitis)
Diarrhea and malabsorption: gluten ataxia, Whipple disease, vitamin E deficiency
Prominent sensory symptoms: B12 deficiency and Friedreich’s ataxia
Peripheral neuropathy: late-onset Tay–Sachs disease, cerebrotendinous xanthomatosis (CTX), ataxia-telangiectasia, Refsum disease, DNA-gamma POLG-polymerase (POLG) mutations, SCA 1, SCA 2, SCA 3, SCA 4, SCA8, SCA12, SCA18, SCA23, and SCA 25
Visual symptoms: SCA7, ataxia with vitamin E deficiency (AVED) and mitochondrial cytopathies
Seizures: paraneoplastic syndrome, DRPLA, and SCA10
Myelopathy with ataxia: Alexander disease, SCA 3, autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), and adult-onset Friedreich’s ataxia.
Tremors: Wilson disease, SCA 12, fragile X-associated tremor/ataxia syndrome
CASE 30-1 (continued)
You know the onset of the condition was later in life with a slowly progressive course. The patient notes he has had considerable problems with visual acuity in addition to his gait. There is a vague family history of some gait and balance problems.
Ataxic conditions manifest in the limbs and during ambulation. In addition, cerebellar disorders present with speech and occulomotor manifestations, which are absent in sensory ataxias:
Limb ataxia: The actions of the limbs are uncoordinated with problems seen with alternating movements (dysdiadochokinesia) and rhythmic tasks.
Dysmetria: Dysmetria or past pointing is the inability to scale a particular movement to reach an intended target. Finger chase test is probably the easiest way to elicit dysmetria in the limbs.
Intention tremor: One can test for intention tremor by asking the patient to perform the nose-finger and heel-shin test. The movement of the limb traces a zigzag to the target. Another way would be to get the patient to do something that requires both spatial and motor coordination, for example pouring water from one cup into another.
Ataxic gait: Ataxic gait resembles the gait of a drunken person in that the gait is wide based and unsteady. Movements are disorganized and clumsy, with frequent lateropulsion and increased risk of falls.
Ocular ataxia and nystagmus: The eye examination should include fixation at a distance and eccentric gaze 30 degrees from midline looking for nystagmus. Down beat nystagmus, periodic alternating nystagmus, and saccadic dysmetria occur with different oculo-cerebellar syndromes. For dysmetria, you can hold your thumb in front of the patient’s face and your finger to the side and ask the patient to look alternately and quickly from thumb to the finger and vice versa. During pursuit task, there is a “square-wave,” jerky movement of the eyes. The saccades could be hypometric or hypermetric.
Cerebellar dysarthria: Cerebellar dysarthria has irregular cadence, pitch, and volume. The best way is simply to listen to the patient. Alternatively using polysyllabic words such as “British Constitution” and “Baby Hippopotamus” said repeatedly can accentuate and bring out the problems more.
Head impulse (or head thrust) maneuver: With the patient sitting on the stretcher, the physician instructs the patient to maintain gaze on the nose of the examiner. The physician then holds the patient’s head steady in the midline axis and then rapidly turns the head to about 20° off the midline. The normal response is for the eyes to stay locked on the examiner’s nose. An abnormal response is elicited if the eyes to move with the head, and then snap back in one corrective saccade to the examiner’s nose. An abnormal test indicates an impaired vestibule-ocular reflex. The test is usually “positive” (ie, corrective saccade is visible) with peripheral lesions (vestibular neuritis), and the test is usually normal in cerebellar structural pathology.4
General examination: A thorough general examination including visual fields, sensory, skin, and musculoskeletal survey completes the targeted examination.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
