Epilepsy - Symptoms, Types, and Treatment

EPILEPSY A seizure is any clinical event caused by an abnormal electrical discharge in the brain, whilst epilepsy is the tendency to have recur- rent seizures. A single seizure is not epilepsy but is an indication for investigation. The recurrence rate after a first seizure approaches 70% in the fir...

EPILEPSY A seizure is any clinical event caused by an abnormal electrical discharge in the brain, whilst epilepsy is the tendency to have recur- rent seizures. A single seizure is not epilepsy but is an indication for investigation. The recurrence rate after a first seizure approaches 70% in the first year. The lifetime risk of a single seizure is ~5%, whilst the prevalence of epilepsy is ~0.5%. The division of seizure types on physiological grounds is bet­ N E U R O L O G I C A L D I S E A S E 16 ween focal seizures in which paroxysmal neuronal activity is lim­ ited to one part of the cortex, and generalised seizures in which the electrophysiological abnormality involves both hemispheres simultaneously. Clinical features To classify seizure type, establish first whether there is a focal onset, and second whether the seizures conform to one of the recognised patterns (Box 16.13). Epilepsy that starts over the age of 35 almost invariably reflects a focal cerebral event. Where activity remains focal, signs may indicate the site. Even when generalised tonic– clonic seizures occur, seizures beginning in one cortical area will cause neurological symptoms and signs corresponding to the func- tion of that area. Occipital onset: causes visual changes (lights/blobs of colour). Temporal lobe onset: false recognition (déjà vu). Sensory strip involvement: sensory alteration (burning, tingling). Motor strip involvement: jerking. Focal seizures These may be idiopathic or may reflect focal structural lesions. The latter may be: Genetic (e.g. tuberous sclerosis). Developmental. Cerebro­ vascular (e.g. arteriovenous malformation). Neoplastic. Traumatic. Infective. Inflammatory (e.g. vasculitis). Focal neurological signs may localise the source, but the signs may spread, causing impairment of awareness or bizarre behaviour. Generalised seizures Tonic–clonic seizures: May be preceded by an initial ‘aura’. The patient then goes rigid, stops breathing, becomes unconscious and cyanosed, and may fall heavily. After a few moments, the rigidity is periodically relaxed, producing clonic jerks. Urinary incontinence or tongue-biting may occur. After a period of flaccid coma, the patient then regains consciousness, but is drowsy or confused for some hours. Absence seizures: Generalised seizures, which always start in childhood. The child goes blank and stares for a few seconds only. The attacks are brief but may be frequent, and are not associated with post-ictal confusion. They may be mistaken for daydreaming. 643  16.13 Classification of seizures (2010 International League Against Epilepsy classification) Generalised seizures Tonic–clonic (in any combination) Absence: Typical Atypical Absence with special features N E U R O L O G I C A L D I S E A S E 16 Myoclonic absence Eyelid myoclonia Myoclonic: Myoclonic Myoclonic atonic Myoclonic tonic Clonic Tonic Atonic Focal seizures Without impairment of consciousness or awareness (was ‘simple partial’): Focal motor Focal sensory With impairment of consciousness or awareness (was ‘complex partial’) Evolving to a bilateral, convulsive seizure (was ‘secondarily generalised seizure’): Tonic Clonic Tonic–clonic Unknown Epileptic spasms Myoclonic seizures: Brief, jerking movements, predominating in the arms. They occur in the morning or on waking, or may be pro- voked by fatigue, alcohol or sleep deprivation. Atonic seizures: Seizures involving brief loss of muscle tone, usually resulting in heavy falls with or without loss of consciousness. Tonic seizures: Associated with a generalised increase in tone and an associated loss of awareness. Atonic and tonic seizures are usually seen as part of an epilepsy syndrome. Clonic seizures: Similar to tonic–clonic seizures, but without a preceding tonic phase. Many patients with epilepsy follow specific patterns of seizure type(s), age of onset and treatment responsiveness: the so-called electroclinical syndromes. Genetic testing may ultimately demon- strate similarities in molecular pathophysiology. 644 Investigations No cause is found in most patients. However, investigations are necessary to confirm the diagnosis, characterise the type of epilepsy, and identify any underlying cause. Cerebral imaging: After a single seizure, head CT or MRI is advis- able, although the yield of structural lesions is low unless there are focal features. EEG: May be more helpful in showing focal features if performed N E U R O L O G I C A L D I S E A S E 16 very soon after a seizure than after an interval. It can also help establish the type of epilepsy and guide therapy; however, an inter- ictal EEG is normal in 50% so it cannot exclude epilepsy. Other investigations: These should identify any metabolic, infec- tive, inflammatory or toxic causes. They include FBC, ESR, CRP, U&Es, glucose, LFTs, CXR, syphilis serology, HIV, tests for collagen disease and CSF examination. Management Explain the nature and cause of seizures to patients and their rela- tives. Instruct relatives in the first aid management of major seizures. Emphasise that epilepsy is common and that full control can be expected in ~70% of patients. The recognised mortality of epilepsy should be discussed sensi- tively with patients to encourage a serious approach to lifestyle modification and adherence to medication. Immediate care: Little can or need be done for a person whilst a major seizure is occurring, except for first aid and common-sense manœuvres (Box 16.14). Lifestyle advice: Patients should be made aware of the riskiness of activities in which loss of awareness would be dangerous, until good control of seizures has been established. This includes work or recreational activities involving exposure to heights, dangerous machinery, open fires or water. In the UK and many other countries, 16.14 Immediate care of seizures First aid (by relatives and witnesses) Move person away from danger (fire, water, machinery, furniture) After convulsions cease, turn into ‘recovery’ position (semi-prone) Ensure airway is clear but do not insert anything in mouth (tongue-biting occurs at onset and cannot be prevented) If convulsions continue for > 5 mins or recur without person regaining consciousness, summon urgent medical attention Person may be drowsy/confused for 30–60 mins and should not be left alone until recovered Immediate medical attention See Box 16.2 645  16.15 Guidelines for choice of anti-epileptic drugs Epilepsy type First-line Second-line Focal onset and/or Lamotrigine Carbamazepine secondary GTCS Levetiracetam Sodium valproate Topiramate Zonisamide N E U R O L O G I C A L D I S E A S E 16 GTCS Sodium valproate Lamotrigine Levetiracetam Topiramate Zonisamide Absence Ethosuximide Sodium valproate Myoclonic Sodium valproate Levetiracetam Clonazepam N.B. Use as few drugs as possible. (GTCS = generalised tonic–clonic seizure.) legal restrictions regarding vehicle driving apply to patients with epilepsy. Anticonvulsant drug therapy (see also p. 761): Drug treatment should be considered after more than one unprovoked seizure. In most patients, full control is achieved with a single drug. Dose regimens should be kept as simple as possible to promote compliance. Guidelines are listed in Box 16.15. For seizures of focal onset, lamotrigine is the best-tolerated monotherapy and has few side-effects. Unclassified or specific syndromes respond best to valproate. Sodium valproate should not be used in women of reproductive age unless the benefits outweigh the risks. The first choice should be an established first-line drug, with more recently introduced drugs as second choice. Newer drugs have predictable pharmacokinetics, so drug levels are mainly used to monitor adher- ence. Gradual medication withdrawal may be considered after 2 seizure-free yrs. Surgery: Some patients with drug-resistant epilepsy respond to resection of epileptogenic foci or nerve stimulation. Prognosis Generalised seizures are more readily controlled than partial sei- zures. A structural lesion makes complete control less likely. After 20 yrs: 50% have been seizure-free for the last 5 yrs without medication. 20% are seizure-free with medication. 30% continue to have sei- zures despite medication. Withdrawal of anticonvulsant therapy: After complete control of seizures for 2–4 yrs, withdrawal of medication may be considered. Childhood-onset epilepsy carries the best prognosis for successful drug withdrawal. Overall, the recurrence rate of seizures after drug withdrawal is ~40%. Withdrawal should be undertaken slowly, reducing the drug dose gradually over 6–12 mths. 646