Unsteadiness/Ataxia

Question 1

Define ataxia.

Answer 1

Incoordination of voluntary movement

Question 2

What are the 2 types of ataxia?

Answer 2

Cerebellar and sensory

Question 3

Describe the location of the cerebellum, in relation to the cerebrum and brainstem.

Answer 3

• Sits in the posterior cranial fossa above the foramen magnum
• Inferior to the occipital and temporal lobes
• Separated from the medulla and pons by the 4th ventricle
• Covered by tentorium cerebelli (dura mater)

Question 4

Describe the structure of the cerebellum.

Answer 4

• 2 hemispheres of the cerebellum are separated down the midline by the cerebellar vermis
• Sulci and fissures further divide the cerebellum into lobes and fissures
• There are 3 main lobes:
  1. Anterior lobe
  2. Posterior lobe
  3. Flocculonodular lobe
• There are 2 main fissures:
  1. Primary fissure (separates anterior + posterior lobes)
  2. Posterolateral fissure (separates posterior and flocculonodular lobes)

Question 5

Which nuclei are found in the lateral hemispheres of the cerebellum?

Answer 5

Dentate nucleus

Question 6

Which nuclei are found in the vermis and intermediate zones of the cerebellum?

Answer 6

Emboliform and Globose nuclei

Question 7

Which nuclei are found in the flocculonodular lobe of the cerebellum?

Answer 7

Vestibular and Fastigial nuclei

Question 8

What is the effect of lesions to the lateral hemispheres of the cerebellum?

Answer 8

• Ipsilateral limb ataxia
• Dysdiadochokinesis
• Dysmetria
• Intention tremor
• Scanning/staccato speech (ataxic dysarthria)

Question 9

What is the effect of lesions to the vermis and intermediate zones of the cerebellum?

Answer 9

• Truncal ataxia (main feature)
• Gait ataxia (main feature)
• Limb ataxia
• Dysdiadochokinesis
• Dysmetria
• Intention tremor
• Hypotonia

Question 10

What is the effect of lesions to the flocculonodular lobe of the cerebellum?

Answer 10

• Vertigo

- Nystagmus (towards side of lesion)

Question 11

What is gait ataxia?

Answer 11

Often described as a wide-based, reeling gait

• more apparent when turning or stopping suddenly

Question 12

What is dysmetria?

Answer 12

In ability to perform acute finger-to-nose movements with past-pointing/similar inability in heel-shin testing

Question 13

What is dysdiadochokinesis?

Answer 13

Inability to perform rapid, alternating movements

Question 14

What is dysarthria?

Answer 14

Slurred speech/difficulty producing speech

• In cerebellar lesions this is typically a scanning/staccato speech where words are broken up into syllables

Question 15

What type of nystagmus is seen in cerebellar lesions?

Answer 15

Coarse nystagmus with fast phase in the direction of the lesion

Question 16

What are the potential causes of cerebellar ataxia?

Answer 16

• Toxic (alcohol)
• Medication (phenytoin, lithium)
• Vascular (ischaemic stroke, haemorrhage)
• Inflammatory (MS, ADEM)
• Neoplastic
• Infectious/post-infectious
• CJD
• Structural (Arnold-Chiari, AVM)
• Degenerative (MSA)
• Nutritional (vit E def, vit B1 def, coeliac)

Question 17

How should sensory ataxia be assessed?

Answer 17

• Joint position sense
• Upper limb position sense loss is tested by attempting to bring both horizontally outstretched index fingers together in the midline with eyes closed
• Heel/shin testing deteriorates with eye closure
• Pseudoathetosis of fingers with arms outstretched and eyes closed
• Positive Romberg’s test

Question 18

What are the potential causes of sensory ataxia?

Answer 18

• CIDP (Miller-Fisher syndrome)
• Friedrich’s ataxia
• Spinal cord disorders (cervical spondylosis, demyelination, B12 def)
• Sensory ganglionitis (paraneoplastic, Sjogren’s)
• Paraproteinaemic neuropathy (IgM)
• Refsum’s disease