Categorizing 1.motor ataxias (isolated lesions of the cerebellum are not the most common cause of these complaints) 2.sensory ataxias
Motor ataxias (cerebellar) usually caused by cerebellar disorders one of the cerebellar hemispheres involvement :the ipsilateral limb
Cerebellar midline portion involvement axial muscle Coordination problem (difficulty maintaining a steady upright standing or sitting posture)
Isolated hemiataxia Supratentorial infarctions, particularly small deep infarctions or lacunae of the posterior limb of the internal capsule interruption of ascending or descending cerebellar to cortical pathways
motor or cerebellar-like ataxia with hemisensory loss Small infarctions or hemorrhages in thalamic nuclei may produce this clinical picture
Sensory ataxias failure in transmission of proprioception or position sense information to CNS. This may arise from disorders affecting the peripheral nerves, spinal cord, or cerebellar input tracts. may be compensated to a degree with visual sensory information. sensory ataxia often worsen in poor lighting conditions
CLINICAL FEATURES Hx:headache, nausea, fever,weakness, or numbness.,medication history, or family history of ataxia
The nature of onset of symptoms and the time course of the process guide the pace of investigations
General physical examination Orthostatic vital signs(hypovolemia, diabetic neuropathy and other neurologic syndromes) Gait testing. Observing :sit upright in the stretcher, rise, stand, walk, and turn around. Walk at a normal speed,on the heels, and then toes.
Tandem gait toe-to-toe walking It tests many elements of the nervous system
Cerebellar functions test perform smooth voluntary movements and rapidly alternating movements; In lateral cerebellum involvement: 1.dyssynergia(breakdown of movements into parts), 2.dysmetria (inaccurate fine movements), 3.dysdiadochokinesia (clumsy rapid movements).
rapid thigh-slapping test pat the thigh with the palm then the back of the same hand in alternating fashion, making a sound with each rapid slap
finger-to-nose test distinguish between cerebellar and posterior column(proprioceptive) lesions. Performing this test with the eyes closed tests proprioception in the upper extremity.
heel-to-shin test A test for cerebellar function that emphasizes the lower extremities. In cerebellar disease, the heel may initially overshoot the other shin or knee, and completes the action with a series of jerky movements. In posterior column disease, there may be difficulty locating the knee, but the movement down the shin typically weaves from side to side or falls off
Stewart-Holmes rebound sign cerebellar function sudden release of the flexed forearm: the individual fails to check the movement. Another example of rebound phenomena is when a tapped outstretched arm oscillates back and forth for several cycles.
positive Romberg sign Ataxia worsens with this loss of visual input suggesting sensory ataxia with a problem of proprioceptive input (posterior column, vestibular dysfunction), or a peripheral neuropathy.
tabes dorsalis (neurosyphilis) Historically, was a common cause of sensory ataxia.
vitamin B12 deficiency should be a consideration in patients with evidence of posterior column disease. If left untreated, an initial unsteady gait may progress to weakness, spasticity, and ataxia. megaloblastic anemia :may be a clue, but the neuropathy may precede the anemia.
Sensory examination in a patient with unsteady movements position or vibration testing (posterior columns), as well as testing sensation to pinprick. Testing of the deep tendon reflexes will serve largely to discover asymmetry or spasticity that might suggest an alternative diagnosis. Acute cerebellar injury may result in muscle hypotonia for a few days or weeks."
Nystagmus is seen in many different disorders due to lesions in a variety of different locations of the CNS, but the presence of nystagmus does suggest that the pathologic process is intracranial and not in the spinal cord or peripheral nervous system
DIAGNOSIS Questions: 1.Is ataxia sensory or motor apraxia 2.Is primary Process systemic or within the nervous system
SPECIAL POPULATIONS THE GERIATRIC PATIENT THE ALCOHOLIC PATIENT CHILDREN
THE GERIATRIC PATIENT A typical constellation includes gait slowing, shortening of the stride, and widening of the base. This results in the appearance of a guarded gait- that is, the gait of someone about to slip and fall.
THE ALCOHOLIC PATIENT: rostral vermis syndrome (Wernicke's disease) If acute motor ataxia is present with con fusion or eye movement abnormalities, the possibility should be considered IV thiamine administration should be initiated promptly.
CHILDREN Exclude: 1.weakness 2.musculoskeletal disorders. Intoxications are a cause of ataxia in children, and the ingestion may be surreptitious. Acute ataxia may follow immunizations, viral illnesses or rarely reported in the preeruptive phase of varicella.
varicella Usually seen in 2- to 4-year-old range the onset of ataxia from the prodromal illness:2 days to 2 weeks Little workup is needed antiviral medications are not indicated.
Mass lesion usually, some abnormality of cranial nerves or strength will be discovered with careful examination. Abnormal ocular movements should increase the suspicion
opsoclonus-myoclonus syndrome Acute ataxia associated with rapid chaotic eye movements (opsoclonus) and myoclonic extremity jerks of the head and extremities This may be a postviral syndrome but is often a paraneoplastic syndrome associated with a neuroblastoma located in the abdomen or chest.
pyruvate decarboxylase deficiency Unusual metabolic disorders Family history may or may not suggest