2.11 - Disorders of the CNS

Question 1

Case 1

Answer 1

A 25-year-old man fell from scaffolding and fractured his spine in the mid-thoracic region. When examined he had no movement in the right leg and proprioception and sensation for fine discriminative touch was impaired below T10 on the right. However, he could feel pain and changes in temperature in his right leg. In contrast his left leg moved normally, had normal touch sensation but retained no sensation for pain or temperature.

Question 2

What is the site and extent of the lesion? Case 1

Answer 2

Mid-thoracic (T10 spinal level) hemisection of the spinal cord (Brown-Sequard syndrome) on the right side

Question 3

Explain the pattern of symptoms in neuroanatomical terms (Case 1)

Answer 3

• interrupts right lateral corticospinal tract projecting to ipsilateral motor neurones and right ascending dorsal column tract from ipsilateral leg
• leads to loss of function below injury
• no loss of pain and temperature in ipsilateral leg because the ascending spinothalamic tract crosses the midline within a few segments of level of entry of sensory information into spinal cord
• spinothalamic tract from the contralateral leg will be interrupted by the lesion - hence loss of pain and temperature sensation in that leg
• ipsilateral loss of motor control = no movement in right leg, as corticospinal pathway crosses in medulla
• fine discriminative touch impaired on the right as dorsal column tract = ipsilateral

Question 4

Is he likely to recover the lost movement and sensation? (Case 1)

Answer 4

• if tracts are completely disrupted, regeneration in CNS is unlikely
• if some parts of the pathways have only been temporarily affected by compression/inflammation at the site of injury there may be some recovery of function after it has subsided
• there may be some synaptic plasticity
• there may be segmental loss of pain and temperature ipsilaterally at the level of injury due to direct damage to the cord and/or nerve receiving the information

Question 5

Case 2

Answer 5

A 75-year-old patient had a stroke, the immediate signs of which were moderate weakness and loss of sensation in the left hand and forearm. During the following weeks the weakness and sensory disturbance resolved, but periodically she had strange sensations in her left hand, such as sudden coldness or feeling of increased pressure. Occasionally the feeling spread up her arm and sometimes these episodes were accompanied by jerking movements of the arm, which she could not control.

Question 6

What was the location of the infarct that led to the initial stroke symptoms?

Answer 6

• right parietal cortex in/close to the primary somatosensory cortex, hence disturbance of sensation in the left hand
• this region is responsible for sensory innervation to the contralateral side of the body - lack of blood flow to this region will cause impaired function

Question 7

What are the strange sensations and jerking movements a sign of? (Case 2)

Answer 7

• active epileptic focus formed as a result of tissue damage from stroke
• jerks caused by propagation of discharge to arm area of motor cortex in frontal lobe

Question 8

What treatment could be given to reduce or prevent these involuntary movements? (Case 2)

Answer 8

Anticonvulsants

Question 9

What is likely to happen if the condition is left untreated? (Case 2)

Answer 9

• seizures may spread to involve the whole motor cortex and even propagate to other hemisphere to produce generalised seizures
• recurring seizures may contribute to neuronal injury within brain - may be associated with cognitive decline and reduced quality of life