CNS Week 5 Epilepsy Flashcards
Define seizure
A transient occurrence of signs and or symptoms due to abnormal excessive or synchronous neuronal activity in the brain
Define epilepsy
A pathologic and enduring tendency to have recurrent seizures
And
By the neuro-biologic, cognitive, psychological and social consequences of this condition
What is the difference between seizures and epilepsy
Seizures are a pathological pattern of neural activity and epilepsy is a tendency to recurrent seizures
What are the 2 main types of seizure
Generalised seizures: starts simultaenously in both hemispheres
Focal seizures: seizure starts in a focus and then spreads
What are the 3 types of common generalised seizures
Typical absence
Myoclonic
Tonic- clonic
What are absence seizures
Mainly childhood in onset
Frequent brief attacks (1-30s)
Sudden loss and return of consciousness
No aura and no post-ictal state
Some involuntary movements
Respond to some anti-epileptic drugs and not others
What are myoclonus seizures
Sudden brief shock like muscle contractions
Usually bilateral arm jerks
Often worse in the mornings
Precipitated by sleep deprivation and alcohol
Respond to particular anti epileptics
Describe tonic clonic seizures
Sudden onset, gasp, fall
Tonic phase with cyanosis
Clonic phase
Post-ictal phase (recovery is not instant)
Tongue bitten and incontinence, fractured shoulder
Noisy breathing
Headache and muscle pain afterwards
What are focal seizures
Often aura or warning at onset
As seizures spreads -> loss of awareness and involuntary movement
Often caused by brain lesions -> tumour, abscess, trauma
Describe temporal lobe seizures
Auras: rising sensation in stomach, olfactory and gustatory hallucinations, deja vu
As the seizure spreads the person suddenly stops and blank stares, loss of responding and awareness, mouth movements, fidgeting or postures- automatisms
What is idiopathic epilepsy
No brain lesions, no intellectual impairment, often generalised seizures
Easy to treat, seizures usually controlled
What is symptomatic epilepsy
Sign of underlying lesion or brain disorder, often cognitive problems, abnormal MRI common
Seizures not controlled
What are the key regulators of neuronal excitability
Non gated ion channels
- resting membrane potential
Voltage gated ion chanels
- Na+, K+, Ca2+, Cl-
Dendrite information processing
Action potential and repolarisation
What are epileptiform discharges due to
Neuronal bursting (an ion channel property)
Synaptic effects (both glutamate and GABA)
Glia effects
Non synaptic effects (eg extracellular K+)
What is epileptogenesis
The process following an injury that leads to the first of a series of spontaenous and recurring seizures
What structural changes occur in epileptogenesis
Cell loss inhibitory
Axonal sprouting
Neurogenesis
Gliosis
Neuro - inflammation
BBB breakdown
What molecular changes occur in epileptogenesis
Neuronal changes (Na, K, Ca, Cl, HCO3)
Neurotransmitter transporters
Neuro-modulators
What functional changes occur in epileptogenesis
Gap junctions
Glia: buffering of extracellular environment
How was the first anti epileptic drug developed (phenytoin)
Electrodes to rodents head
Shocked with electricity to induce seizure
Loaded with drug beforehand to see if it prevents electrical current from causing a seizure
Mode of action of vigabatrin
GABA transaminase inhibitor
Higher GABA levels prevent fading of inhibiton
Mode of action of tiagabine
GABA reuptake inhibitor
Higher GABA levels prevent fading of inhibition
In summary what are seizures caused by
Abnormal burst firing and synchronisation in normal / modified neural circuits
Steps for the management of epilepsy
Ensuring a correct diagnosis
Determining the cause
Deciding on treatment
Advising on lifestyle issues
4 different types of seizures
Absences
Myoclonus
Tonic clonic
Focal
Differentials for blackouts and funny turns
Epilepsy
Fainting
Cardiac causes
Psychological causes
Why is valporate a risk in women
Has a 6-10% malformation rate in pregnancy with subtle facial abnormalities
30-40% associated with low IQ and autism
Never give valporate to a woman 12-55 without specialist adivce
There is a valporate pregnancy prevention program where it is not prescribed unless the woman is fitted with a highly active contraceptive coil
Non pharmacological epilepsy treatments
Resection of epileptic focus
Vagal nerve stimulation
Ketogenic diet
Social consequences of epilepsy
Loss of driving licence
Loss of employment
Stigmatization and anxiety
Needing antiepileptic drugs
Problems with contraception and conception
Describe idiopathic epilepsy
Milder
No lesion
Easier to control
Often generalised
Describe symptomatic epilepsy
Can vary with age:
- brain malformations
- inherited metabolic / gene disorders
- birth trauma / stroke
- infection and immune disorders
- trauma
- tumours
- stroke
What is language lateralisation
Most humans (70-95%) have a left hemisphere lateralisation for language abilities
Broca identified area in left hemisphere that plays primary role in speech production
Wernicke identified another part of left hemisphere associated with speech comprehension
Different tests used for determining language lateralisation
Wada test
Functional imaging
Event related potentials
Transcranial magnetic stimulation
Describe the wada / sodium amytal test
Procedure used by neuropsychologists prior to surgery for temporal lobe epilepsy to determine hemispheric specialisation for key language skills
Injection of sodium amytal into 1 of the hemispheres produces transient ipsilateral hemiparesis
- when the speech dominant hemisphere is injected there is clear but transient speech impairment
What are the 4 types of hearing impairment
Normal hearing: you can hear quiet sounds of less than 20dB
Mild hearing loss: loss between 20-40 dB
(Difficulty following speech in noisy situations
Moderate hearing loss: between 41-70 dB
(Difficulty following speech)
Severe hearing loss: between 71-95 dB
(Severe difficulty following speech without a hearing aid)
Describe the make up of the external auditory meatus
Lateral third- cartilaginous, ceruminous and sebaceous glands produce cerumen (earwax)
Medial 2/3s - bony lined with thin skin continuous with the tympanic membrane
What is the tympanic membrane
Thin semitransparent membrane externally lined by thin skin and internally lined by mucous membrane all sandwiching radial and circumferential collagen fibres
Measurements of the tympanic membrane
Not quite 1cm across and 0.1mm thick
What are the 3 ossicles
Malleus (hammer) 8mm, 0.025g
Incus (anvil) 10mm, 0.025g
Stapes (stirrup) 3x1mm, 0.002g
Combined role of the ossicles
Increase the force and reduce the amplitude of vibrations needed to drive the inner ear
What is the stapedius
The bodys smallest muscle. Inserts to the stapes and when tense reduces the amplitude of vibrations
What is the tensor tympani
Inserts into the malleus and when tense it reduces the amplitude of the vibrations
Describe the process of ear syringing
Used to clear blocked ear canals from wax
Water 37c is forced into the external auditory meatus
Aimed posterosuperiorly to prevent perforation of the tympanic membrane
Hold a bowl inferiorly to the auricle to catch any material dislodged from the meatus including the returning water
What are otoscopes
Used to view the tympanic membrane
Straighten out the meatus by pulling the tip of the pinna posteriorly and superiorly
Use little finger against the patients cheek as a guage of depth
3 problems that can arise in the external auditory meatus
Wax: 50% skin, 50% cerumen which is translucent on secretion but turns yellow golden brown black in time
Otitis externa: inflammation of the ear canal- eg caused when a foreign body becomes dislodged
Bony growths: arise by the formation of the benign new bone
2 conditions that can arise in the tympanic membrane
Tympanosclerosis- scarring of the tympanic membrane causing calcium deposits to form
Perforation in the membrane
What is conductive hearing loss
Loss by air conduction but not by bone conduction (an air borne gap)
Generally indicates a problme in the outer / middle ears that hinders normal sound getting ot the inner ear
Can usually be fixed by ENT surgery
What is otitis media and how can it be treated
Inflammation of the mucus membrane lining the middle ear
Treated by a grommet surgically inserted in the tympanic membrane (commonest surgery for young children)
What are some abnormalities of the outer ear
Microtia: congenital abnormality. Failure of the auricle and external auditory meatus to develop
Pre-auriciular appendage - accessory cartilaginous appendage formed just anterior and superior to the tragus
Haematoma- result of blunt trauma causing subcutaenous bleeding (cauliflower ear)
Describe the method of sound delivery
The outer hair cells actively amplify sounds
Which releases energy into the cochlea
Which vibrate everything in reverse order
Which vibrates the eardrum and so vibrates the air
Which is sound emissions
What is tinnitus
The conscious perception of an auditory sensation in the absence of a corresponding external stimulus
No treatment to successfully eliminate
Negatives of hearing aids
They dont restore normal hearing
They dont sound natural or transparent
Dont distinguish wanted vs unwanted sounds
Dont properly fix the difficulty focusing on wanted sounds
Features of a temporal lobe seizure
Olfactory hallucinations (imagining smells) and smacking lips together
Features of an occipital lobe seizure
Flashes / floaters
Features of a juvenile myoclonic seizure
Infrequent generalised seizures and daytime absences
Features of a parietal lobe seizure
Paraesthesia (burning or prickling sensation in hands, arms, legs or feet)
Features of frontal lobe seizures
Posturing and head / leg movements
Symptoms of idiopathic intracranial hypertension
Blurred vision and headache worsened by coughing and changing position
Difficulty abducting right eye (lateral rectus eye muscle impaired)
and bilateral papilloedema visible on fundoscopy
Classically seen in overweight women
Symptoms of giant cell arteritis
Left sided vision loss, headache and scalp tenderness
High temperature
Jaw claudication
Relative afferent pupillary defect
Treatment for giant cell arteritis
High dose prednisolone
Which monoclonal antibody treatment is directed against vascular endothelial growth factor (VEGF)
Bevacizumab
What is conduction dysphasia
Fluent speech but poor repetition with relatively intact comprehension
Is the result of a lesion to the arcuate fasciculus which connects broca and wernicke’s areas
What is drusen
Yellow deposits on the retina
Is a characteristic sign of dry age related macular degeneration
Role of astrocytes
Remove excess potassium ions from CSF in the CNS
Provide physical support for neurons
Help form BBB
Help with physical repair of neuronal tissues
What neurotransmitter is involved in photophobia, lacrimation and redness and pupil constriction
Acetylcholine
As these are parasympathetic pathway activity and acetylcholine is the main transmitter of this pathway
What is the ordinary function of ependymal cells
Provide the inner lining of the ventricles and are responsible for CNS production
