Central Nervous System Tutorial

Question 1

what is a hemisection of the spinal cord?

Answer 1

Hemisection of the spinal cord results in the distinctive syndrome of ipsilateral paralysis and contralateral pain and temperature loss below the level of the lesion, known as the Brown-Séquard syndrome. Although often not as prominent clinically, ipsilateral vibration and proprioceptive loss also occurs (on the same side as the motor symptoms). Occurs one the right or left hand side of the spinal cord.

Question 2

Can someone recover from a hemisection?

Answer 2

If the tracts are completely disrupted it is very unlikely that there will be any regeneration
in the CNS. However, if some parts of the pathways have only been temporarily affected
by compression or inflammation at the site of injury there may be some recovery of
function after this has subsided. There may also be some synaptic plasticity.

Question 3

Two further points which students may raise if they have been reading the textbooks:

Answer 3

Additionally, there may be segmental loss of pain and temperature ipsilaterally at the
level of the injury due to direct damage to the cord and/or nerve receiving the
information.
Loss of pain on the side contralateral to the injury may begin a few segments below the
level of the lesion because most spinothalamic fibres ascend for a few segments before
crossing over the mid-line. Thus, the fibres originating at the level of the lesion are spared.

Question 4

Case 2
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 he had strange sensations in his left hand,
such as sudden coldness or feeling of increased pressure. Occasionally the feeling spread up
his arm and sometimes these episodes were accompanied by jerking movements of the arm,
which he could not control.

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

What treatment could be given to reduce or prevent these involuntary movements?

What is likely to happen if the condition is left untreated?

Answer 4

affects pre-central gyrus/ primary motor cortex (loss of motor function)
and post-central gyrus/ primary somatosensory cortex (loss of sensation)
moderate weakness but still able to move left hand and forearm
so stroke must be in the primary somatosensory cortex (post-central gyrus) in the right hemisphere, but as the primary motor cortex is directly adjacent, then movement will also be affected.
exact location depends on somatotopy - superior section of primary somatosensory cortex
will be on the right side of the brain as all sensory and motor neurons decussate to the left side by the time you get to the nerve that innervates the left arm

induced epilepsy - synapses are not working effectively and are sending out extra impulses
Acute ischemia leads to increased extracellular concentrations of glutamate, an excitatory neurotransmitter that has been associated with secondary neuronal injury.2,4 Recurrent epileptiform-type neuronal discharges can occur in neural networks of surviving neurons exposed to glutamate. 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.

anticonvulsants

Seizures may spread to involve whole motor cortex and even propagate to other
hemisphere to produce generalised seizures.