W3 Epilepsy and Neuroplasticity

Question 1

Epilepsy definition

Answer 1

‘A chronic medical condition produce by temporary changes in the electrical function of the brain, causing seizures which affect awareness, movement, or sensation.’

Question 2

Types of Epilepsy

Answer 2

Partial Epilepsy: Simple partial seizures + Complex partial seizures.
Generalized Epilepsy: Grand mal seizures + Petit Mal seizures.

Question 3

Epilepsy: Simple Partial seizures

Answer 3

Localized, effects that are usually sensory and/or motor. Jerking beginning in righ hand and progressing to clonic movements of entire arm, produced by epileoptiform activity in the motor cortex that controls the armS.

Question 4

Epilepsy: Complex partial seizures

Answer 4

localized, complex and diverse effect, imaired awareness seirues. May be associated with apparently ordered corrdinates by innapropriate motor beheaviour (running, chewing ect.) may be absent, lasts few minutes, no memory of episode.

Question 5

Epilepsy: Aurus

Answer 5

symptom preceding partial seizures. Auras are abnormal sensations, (e.g = sense of fear, rising feeling in abdomen, strange tastes or odours ‘metallic’, visual sensations akin to hallucinations). Aura due to early abnormal electrical activity originating from seizure focus - earliest manifestation of partial seizure.

Question 6

Epilepsy: Petit Mal (absence)

Answer 6

Can involve entire brain (‘generalized’). The person is briefly “absent”, disrupted consciousness (may not know they were absent). More common in children, often disappear with age.

Question 7

Epilepsy: Grand Mal seizures

Answer 7

Can involve entire brain (‘generalized’). Patients may lose consciousness, fall to ground, rigidly extend all limbs (tonic phase), then have jerks in all extremities (clonic phase). Tonic-clonic seizure or ‘Grand mal’.

Question 8

What happens to the brain during a seizure?

Answer 8

EGG detects synchronized activity of many neurons ‘field potentials. Diagnosis based on EEG measures, plus neuropsychological symptoms.

Question 9

Epilepsy: Treatments: Pharmacological

Answer 9

carbamazepine, phenobarbital, phenytoin
(Dilantin), valproic acid
Drugs that target GABA or Na+ channels
The above strategies seek to dampen down the excessive neural firing ,e.g. increasing release of the inhibitory neurotransmitter GABA in a way not unlike some general anaesthetics

Question 10

Neuroplasticity

Answer 10

Changes to brain structure, connectivity and function over time in response to changing environment (internal or external). Akin to ‘evolution’, in the sense that what already exists is modified to better suit requirements.
Key Principles
1. Neurodegeneration
2. Neural Regeneration
3. Neural Reorganization

Question 11

Neuroplasticity: neurodegeneration

Answer 11

Grey matter volume decline w/age, due to reduction in connections and in numbers of other support cells.
White matter volume increases for a while as the connections get better insulated with myelin – connections to/from frontal cortex amongst the last to become fully myelinated.

Question 12

Causes of Neurodegeneration

Answer 12

Disruption of normal neurotransmitter function (e.g. loss of input, excitotoxicity). Loss of fuel supply (oxygen, glucose). Attack from infections, toxins or own immune system.
Faulty genetic signalling.
Physical injury
Neuronal death: necrosis, apoptosis

Question 13

Neuroplasticity: Neuronal death

Answer 13

Body parts that are chopped off do not grow back in mammals but there’s a clear capacity for regrowth/regeneration in the peripheral nervous system (PMS), but it is more complex in the central nervous system (CNS).

Question 14

CNS

Answer 14

central nervous system = brain, spinal cord.

Question 15

PNS

Answer 15

Peripheral nervous system: everything else - located outside the skull and spine. Two Divisions
1- Somatic nervous system = part that interacts with the external environment. [sensory signal, afferent nerves]==>[motor command, efferent nerves] CNS
2-Automatic nervous system. = part that regulates the body’s internal environment internal organs ==><== CNS

Question 16

Assuming the cause of degeneration has been resolved.

Answer 16

The presence of Schwann cells appears critical for regeneration (regrowth) of PNS neurons. That, and distance to the target, are key factors in whether there is effective regeneration. Regrowth is not always helpful – the wiring gets messed up if the remaining Schwann cells are not able to guide it properly

Question 17

Implications for spinal cord injury

Answer 17

Regeneration potential for seriously injured spinal cord neurons therefore much reduced. Whereas. Peripheral nerve targets such as muscle stand a much better chance.
Treatment strategies tend to focus on guiding regrowth and enhancing the tissue environment. (in part, trying to support or replicate the existing PNS strategies)

Question 18

Neuroplasticity: Neural Reorganization

Answer 18

Representations are more complex and overlapping – this is a good thing for neural re-organisation following damage. After all, few motor commands require isolated activation of a single muscle or small group of muscles.