NEUROLOGY(D)

 

A1.

Occurrence of seizure due to brain stroke:

·         Cells in the brain send electrical signals to one another

·         The electrical signals pass along your nerves to all parts of the body

·         A sudden abnormal burst of electrical activity in the brain can lead to the signals to the nerves being disrupted, causing a seizure

·         This electrical disturbance can happen because of stroke damage in the brain.

·         A seizure can affect vision, smell and taste, loss of consciousness and jerking movements.

Mechanism of seizure activity:

·         You’re more likely to have a seizure if you had a haemorrhagic stroke (bleed on the brain).

·         Seizures can also be more likely if you had a severe stroke, or a stroke in the cerebral cortex, the large outer layer of the brain where vital functions like movement, thinking, vision and emotion take place.

·         Some people will have repeated seizures, and be diagnosed with epilepsy.

·         The chances of this happening may depend on where the stroke happens in the brain and the size of the stroke.

·         There are several causes for early onset seizures after ischaemic strokes.

·         An increase in intracellular Ca2+ and Na+ with a resultant lower threshold for depolarisation, glutamate excitotoxicity, hypoxia, metabolic dysfunction, global  hypo perfusion and hyper perfusion injury ,(particularly after carotid end arterectomy) have all been postulated as putative neurofunctional aetiologies.

·         Seizures after haemorrhagic strokes are thought to be attributable to irritation caused by products of blood metabolism.

·         The exact pathophysiology is unclear, but an associated ischaemic area secondary to haemorrhage is thought to play a part.

·         Late onset seizures are associated with the persistent changes in neuronal excitability and gliotic scarring is most probably the underlying cause.

·         Haemosiderin deposits are thought to cause irritability after a haemorrhagic stroke.

·         In childhood, post‐stroke seizures can occur as part of perinatal birth trauma.

 

 

A2.

Normally the “consciousness system”—a specialized set of cortical-subcortical structures—maintains alertness, attention and awareness. Diverse seizure types including absence, generalized tonic-clonic and complex partial seizures converge on the same set of anatomical structures through different mechanisms to disrupt consciousness.