Cerebellar Signs including Cerebellar Ataxia

See related article Cerebellar Disorders

The cerebellum can be divided into central structures (lingula, vermis and flocculonodular lobe) and the cerebellar hemispheres. Main inputs come from frontopontocerebellar connections (contralateral) from above, and spinocerebellar tracts from below (proprioception) producing primarily ipsilateral signs.

Midline lesions can produce severe gait and truncal ataxia. As they extend, they can also give fourth cranial nerve lesions and severe ipsilateral arm tremor, marked nystagmus, vertigo and vomiting, and can block CSF flow (obstructive hydrocephalus).

Cerebellar hemisphere lesions can produces classic ipsilateral limb ataxia (intention tremor, past pointing and mild hypotonia). Limb rebound can be demonstrated by gently pushing down on outstretched arms and then suddenly releasing, causing the arm on the affected side suddenly to fly upwards. Lateral lesions tend to produce more subtle nystagmus (maximal looking towards side of lesion)

Lesions of the midline vermis of the cerebellum cause truncal ataxia, while lesions of the cerebellar hemispheres cause limb ataxia of the ipsilateral side.²

Gait ataxia¹

Patients will tend to stand with feet well apart and are often frightened to stand. Patients tend to reel to the side of unilateral lesion, or from side to side if central or bilateral (even if supported). Walking along a line of the floor demonstrates minor degrees of gait ataxia. Wobbling may increase if eyes are closed but patients don't fall - this is not a true "positive Romberg's test" (which is positive when there is impaired joint proprioception).

Truncal ataxia¹

Patients can't sit or stand unsupported and tend to fall backwards. It is caused by a midline cerebellar lesion, or may be a feature of post-chickenpox cerebellar syndrome. Truncal tremor may be evident - constant jerking of trunk and head.

Limb ataxia¹

Lesions of the cerebellar hemisphere cause ipsilateral signs. The outstretched arm tends to be held hyperpronated at rest and at a slightly higher level than unaffected side (Riddoch's sign), and rebounds upwards if gently pressed downwards and then suddenly released by the examiner. Finger-nose and heel-knee-shin tests will demonstrate even mild limb ataxia, with terminal intention tremor and dysmetria (past pointing).

Cerebellar dysarthria

Cerebellar disease can produce a spluttering staccato speech. Scanning dysarthria - jerky and explosive speech with separated syllables may be demonstrated by asking the patient to repeat "baby hippopotamus".

Writing

This may be larger than normal (contrast with micrographia of Parkinson's disease).

Rapid alternating movements

Cerebellar lesions produce inaccuracies in rapidly repeated movements (dysdiadochokinesia). This is demonstrated by getting the patient to tap the back of their own hand repeatedly with the other hand, or to tap their foot on the floor.

Tremor

Cerebellar lesions can produce unilateral or bilateral intention tremor, or a truncal tremor.

Nausea and vomiting

Cerebellar lesions can produce nausea and/or vomiting. Sudden vomiting (without warning) after a positional change, without preceding nausea, is suggestive of a posterior fossa lesion.¹ There may be other signs secondary to obstructive hydrocephalus.

• Check eye movement - looking for ophthalmoplegia or nystagmus
• Check fundi for papilloedema
• Get patient to stick their tongue out and move it from side to side (movement slowed)
• Ask patient to repeat "baby hippopotamus" - look for dysarthria and abnormal speech rhythm and syllable emphasis
• Examine arms for limb ataxia (see above): rebound of outstretched arms, finger-nose test for past pointing, check for dysdiadochokinesis
• Examine leg co-ordination with heel-shin test
• Check limb power, tone and reflexes - cerebellar disorders may produce mild hypotonia and hyporeflexia
• Ask patient to sit up with arms crossed - looking for truncal ataxia
• Ask patient to walk heel-to-toe (to elicit any gait ataxia)
• Get patient to stand with feet together - patients with cerebellar disorders will be unsteady with eyes open and closed (not a true Romberg's positive)
• If unilateral signs - check V, VII, and VIII (cerebellopontine angle pathology)