Ataxia

Source: Wikipedia

Ataxia = lack of coordination of movements.

Types = cerebellar, sensory, vestibular.

Cerebellar

Vestibulocerebellar: Eye movements; causes postural instability. The patient tends to separate her feet when standing to avoid body oscillations (especially forward-backward ones. The instability is therefore worse when standing with feet together, regardless of whether the eyes are open or closed (eyes are defective). Romberg's test is negative, denoting the patient's inability to carry out the test because she feels unstable even with open eyes.

Spinocerebellar: Body and limb movements; causes wide-based 'drunken sailor' gait.

Cerebrocerebellar: Voluntary, planned movements:

• Intention tremor (could involve the head and eyes and torso and limbs).
• Handwriting abnormality: Large unequal letters; irregular underlining.
• A particular pattern of dysarthria: Slurred speech, sometimes characterised by explosive variations in voice intensity despite a regular rhythm.

Sensory

Ataxia due to loss of proprioception. Usually caused by dysfunction of the dorsal columns of the spinal cord. However, the cause may also be dysfunction of the parts of the brain that receive postural information, including the thalamus, cerebellum, parietal lobes.

• Unsteady, 'stomping' gait with heavy heel strikes.
• Postural instability that is worsened when there is no visual input, e.g. poorly lit environment. Romberg's positive.
• Worsening of the finger-pointing test with eyes closed.
• Pyramidal (corticospinal) drift when eyes are closed. The patient's arms will tend to drop and then be restored to the horizontal extended position by sudden muscular contractions (the 'ataxic hand').

Vestibular

Symptoms of vestibular dysfunction:

• Acute & unilateral: Vertigo, nausea, vomiting.
• Chronic & bilateral: Vertigo, nausea and vomiting may be absent. Dysequilibrium may be the sole presentation.

Thunderclap headache = SUMMIT

Causes of thunderclap headache:

• SAH 25%.
• Unknown - no cause found in 50-60%.
• Meningitis.
• Migraine.
• Intracerebral bleeds.
• Cortical vein thrombosis.

OHCM 482

Lucid interval

Differential diagnosis of lucid interval: CECE

Carotid dissection

Extradural (epidural) haemorrhage

CO poisoning

Epilepsy

LMN lesions

• Wasting of affected muscles.
• Fasciculation (spontaneous involuntary twitching) of affected muscles.
• Hypotonia/flaccidity
• Reflexes are reduced or absent.
• Plantars remain flexor.

Chief differential diagnosis = weakness from a primary muscle disease, in which:

• Loss is symmetrical.
• Reflexes are lost later than in neuropathies.
• There is no sensory loss!

Myasthenia gravis causes weakness worsening with use (fatiguability); there is little wasting, normal reflexes, and no sensory loss.

UMN lesions

Damage to motor pathways anywhere from the precentral gyrus of the frontal cortex, to the internal capsule, brainstem, cord, anterior horn cells in the cord.

UMN lesions affect muscle groups, not individual muscles.

Weakness is typically 'pyramidal' in distribution.

• UL extensors are weak.
• LL flexors are weak.
• No muscle wasting.
• Loss of fine finger movements may be greater than expected from the overall grade of weakness.
• Spasticity in stronger muscles. Spasticity = increased tone that is velocity-dependent (in rigidity, increased tone is independent of velocity - it is constant throughout passive movement) and non-uniform (resistance to passive movement that can suddenly be overcome - clasp-knife feel).
• Hyperreflexia (reflexes are brisk).

The reflexes in UMN lesions:
- Babinski sign positive (plantars are upgoing).
- Clonus.
- Hoffman's reflex positive. Neck extension is said to increase sensitivity of this test.

NB: UMN lesions can mimic LMN lesions in the first few hours before the spasticity and hyperreflexia develop.

'Extrapyramidal'

'Extrapyramidal' denotes CNS motor phenomena relating to the basal ganglia.

Basal ganglia's main components = SSSP: Striatum, subthalamic nucleus, substantia nigra, pallidum.

Extrapyramidal lesions cause abnormality with initiation and maintenance of movement. Extrapyramidal symptoms = tremor, rigidity, involuntary movements, dyskinesia (e.g. chorea, athetosis, ballismus, dystonia).

• Dyskinesia = Difficulty or abnormality in performing voluntary muscular movements.
• Chorea = Jerky, involuntary movements, chiefly of the face and extremities.
• Athetosis = Slow, involuntary, wormlike movements of the fingers, toes, hands, and feet.
• Ballismus = Twisting, shaking, and jerking motions.
• Dystonia = Abnormal tone.

Symptoms NOT suggestive of extrapyramidal lesions =

• Bradykinesia/akinesia (slow/absent movement)
• Loss of postural reflexes.
  

Cataplexy

Cataplexy = drop attack triggered by emotion.