Seizures & Epilepsy
advertisement
Seizures & Epilepsy MBBS IV Group C Tutor: Prof. V. Wong 16th Feb 2004 Outline Definitions Pathophysiology Aetiology Classification Video demonstration Diagnostic approach Treatment Quiz Definition Seizure • (Convulsion) Clinical manifestation of synchronised electrical discharges of neurons Epilepsy • Present when 2 or more unprovoked seizures occur at an interval greater than 24 hours apart Definition Provoked seizures Seizures induced by somatic disorders originating outside the brain E.g. fever, infection, syncope, head trauma, hypoxia, toxins, cardiac arrhythmias Definition Status epilepticus (SE) Idiopathic SE Continuous convulsion lasting longer than 30 minutes OR occurrence of serial convulsions between which there is no return of consciousness Seizure develops in the absence of an underlying CNS lesion/insult Symptomatic SE Seizure occurs as a result of an underlying neurological disorder or a metabolic abnormality Aetiology of seizures Epileptic Idiopathic (70-80%) Cerebral tumor Neurodegenerative disorders Neurocutaneous syndromes Secondary to Cerebral damage: e.g. congenital infections, HIE, intraventricular hemorrhage Cerebral dysgenesis/malformation: e.g. hydrocephalus Aetiology of seizures Non-epileptic Febrile convulsions Metabolic Hypoglycemia HypoCa, HypoMg, HyperNa, HypoNa Head trauma Meningitis Encephalitis Poisons/toxins Aetiology of Status Epilepticus Prolonged febrile seizure Idiopathic status epilepticus Most common cause Non-compliance to anti-convulsants Sudden withdrawal of anticonvulsants Sleep deprivation Intercurrent infection Symptomatic status epilepticus Anoxic encephalopathy Encephalitis, meningitis Congenital malformations of the brain Electrolyte disturbances, drug/lead intoxication, extreme hyperpyrexia, brain tumor Pathophysiology Still unknown Some proposals: Excitatory glutamatergic synapses Excitatory amino acid neurotransmitter (glutamate, aspartate) Abnormal tissues — tumor, AVM, dead area Genetic factors Role of substantia nigra and GABA Pathophysiology Excitatory glutamatageric synapses And, excitatory amino acid neurotransmitter (glutamate, aspartate) These are for the neuronal excitation In rodent models of acquired epilepsy and in human temporal lobe epilepsy, there is evidence for enhanced functional efficacy of ionotropic N-methyl-D-aspartate (NMDA) and metabotropic (Group I) receptors Chapman AG. Glutatmate and Epilepsy. J Nutr. 2000 Apr; 130(4S Suppl): 1043S-5S Pathophysiology Abnormal area These tissues — tumor, AVM, dead regions of the brain may promote development of novel hyperexcitable synapses that can cause seizures Pathophysiology Genetic factors At least 20 % Some examples Benign neonatal convulsions--20q and 8q Juvenile myoclonic epilepsy--6p Progressive myoclonic epilepsy--21q22.3 Pathophysiology Role of substantia nigra Studies with 2-deoxyglucose indicate that a marked increase in metabolic activity in SN is a common feature of several types of generalized seizures; it is possible that some of this increased activity is associated with GABAergic nerve terminals that become activated in an attempt to suppress seizure spread. Because GABA has been shown to inhibit nigral efferents, it is likely that GABA terminals inhibit nigral projections that are permissive or facilitative to seizure propagation From Gale K. Role of the substantia nigra in GABAmediated anticonvulsant actions. Adv Neurol.1986;44:343-364 Pathophysiology Premature brain It is more susceptible to specific seizures than is the brain in older children and adults Kindling Repeated subconvulsive stimulation (e.g. to the amygdala) will lead to generalized convulsion This may explain the development of epilepsy after injury to the brain One temporal lobe seizure -> contralateral lobe Classification of seizures Seizures Partial Generalized – Electrical discharges in a relatively small group of dysfunctional neurones in one cerebral hemisphere – Diffuse abnormal electrical discharges from both hemispheres – Aura may reflect site of origin – Symmetrically involved – + / - LOC – No warning – Always LOC Partial Seizures Simple 1. w/ motor signs 2. w/ somatosensory symptoms 3. w/ autonomic symptoms 4. w/ psychic symptoms Complex 1. simple partial --> loss of consciousnes s 2. w/ loss of consciousnes s at onset Secondary generalized 1. simple partial --> generalized 2. complex partial --> generalized 3. simple partial --> complex partial --> generalized Simple partial seizures with motor signs Focal motor w/o march Focal motor w/ march Versive Postural Phonatory Simple partial seizures with motor signs Sudden onset from sleep Version of trunk Postural Left arm bent Forcefully stretched fingers Looks at watch Note seizure Simple partial seizures with sensory symptoms Somato-sensory Visual Auditory Olfactory Gustatory Vertiginous Simple partial seizures with sensory symptoms Vertiginous symptoms “Sudden sensation of falling forward as in empty space” No LOC Duration: 5 mins Simple partial seizures with autonomic symptoms Vomiting Pallor Flushing Sweating Pupil dilatation Piloerection Incontinence Simple partial seizures with autonomic symptoms Stiffness in L cheek Difficulty in articulating R side of mouth is dry Salivating on the L side Progresses to tongue and back of throat Simple partial seizures with psychic symptoms Dysphasia Dysmnesic Cognitive Affective Illusions Structured hallucinations Simple partial seizure with pyschic symptoms Dysmnesic symptoms “déjà-vu” Affective symptoms fear and panic Cognitive Structured hallucination living through a scene of her former life again Complex Partial Seizures Simple partial onset followed by impaired consciousness with or without automatism With impairment of consciousness at onset with impairment of consciousness only with automatisms Simple Partial Seizures followed by Complex Partial Seizures Seizure starts from awake state Impairment of consciousness Automatisms lip-smacking right leg Complex Partial Seizures with impairment of consciousness at onset Suddenly sit up Roll about with vehement movement Partial Seizures evolving to Secondarily Generalised Seizures Simple Partial Seizures to Generalised Seizures Complex Partial Seizures to Generalised Seizures Simple Partial Seizures to Complex Partial Seizures to Generalised Seizures Simple Partial Seizures to Generalised Seizures Turns to his R with upper body and bends his L arm Stretches body LOC Tonic-clonic seizure Relaxation phase Postictal sleep Simple Partial Seizures to Complex Partial Seizures to Generalised Seizures Initially unable to communicate but understands Automatism Smacking Hand-rubbing Abolished communication Generalised tonicclonic seizure Generalized seizures Absence Myoclonic Clonic Tonic Tonic-clonic Atonic Absence seizures Sudden onset Interruption of ongoing activities Blank stare Brief upward rotation of eyes Duration: a few seconds to 1/2 minute Evaporates as rapidly as it started Absence seizures Stops hyperventilating Mild eyelid clonus Slight loss of neck muscle tone Oral automatisms Myoclonic seizures Sudden, brief, shock-like Predominantly around the hours of going to or awakening from sleep May be exacerbated by volitional movement (action myoclonus) Myoclonic seizures Symmetrical myoclonic jerks Clonic seizures Repetitive biphasic jerky movements Repetitive vocalisation synchronous with clonic movements of the chest (mechanical) Venous injection of diazepam Passes urine Tonic seizures Rigid violent muscle contraction Limbs are fixed in strained position patient stands in one place bends forward with abducted arms deep red face noises - pressing air through a closed mouth Tonic seizures Elevates both hands Extreme forward bending posture Keeps walking without faling Passes urine Tonic-clonic seizures (grand mal) Tonic Phase Sudden sharp tonic contraction of respiratory muscle: stridor / moan Falls Respiratory inhibition cyanosis Tongue biting Urinary incontinence Clonic Phase Small gusts of grunting respiration Frothing of saliva Deep respiration Muscle relaxation Remains unconscious Goes into deep sleep Awakens feeling sore, headaches Tonic-clonic seizures Tonic stretching of arms and legs Twitches in his face and body Purses his lips and growls Clonic phase Atonic seizures Sudden reduction in muscle tone Atonic head drop Epilepsy syndrome Epilepsy syndromes may be classified according to: Whether the associated seizures are partial or generalized Whether the etiology is idiopathic or symptomatic/ cryptogenic Several important pediatric syndromes can further be grouped according to age of onset and prognosis EEG is helpful in making the diagnosis Children with particular syndromes show signs of slow development and learning difficulties from an early age Table 1. Modified ILAE Classification of Epilepsy Syndromes Category Localization-related Generalized Idiopathic Benign epilepsy of childhood with centrotemporal spikes (benign rolandic epilepsy) Benign occipital epilepsy Benign myoclonic epilepsy in infancy Childhood absence epilepsy Juvenile absence epilepsy Juvenile myoclonic epilepsy Symptomatic (of underlying structural disease) Temporal lobe Frontal lobe Parietal lobe Occipital lobe Early myoclonic encephalopathy Cortical dysgenesis Metabolic abnormalities West syndrome Lennox-Gastaut syndrome Cryptogenic Any occurrence of partial seizures without obvious pathology Epilepsy with myoclonic absences West syndrome (with unidentified pathology) Lennox-Gastaut syndrome (with unidentified pathology) Table 1. Modified ILAE Classification of Epilepsy Syndromes (cond’) Special syndromes Febrile convulsions Seizures occurring only with toxic or metabolic provoking factors Neonatal seizures of any etiology Acquired epileptic aphasia (Landau-Kleffner syndrome) Three most common epilepsy syndromes: 1. Benign childhood epilepsy 2. Childhood absence epilepsy 3. Juvenile myoclonic epilepsy Three devastating catastrophic epileptic syndromes: 1. West syndrome 2. Lennox-Gastaut syndrome 3. Landau Kleffner Syndrome Benign childhood epilepsy with centrotemporal spike (Benign Rolandic Epilepsy) 1. 2. Typical seizure affects mouth, face, +/- arm. Speech arrest if dominant hemisphere, consciousness often preserved, may generalize especially when nocturnal, infrequent and easily controlled Onset is around 3-13 years old, good respond to medication, always remits by mid-adolescence Childhood absence epilepsy 1. 2. 3. 4. 5. School age ( 4-10 years ) with a peak age of onset at 6-7 years Brief seizures, lasting between 4 and 20 seconds 3Hz Spike and wave complexes is the typical EEG abnormality Sudden onset and interruption of ongoing activity, often with a blank stare. Precipitated by a number of factors i.e. fear, embarrassment, anger and surprise. Hyperventilation will also bring on attacks. Juvenile myoclonic seizure 1. 2. 3. Around time of puberty Myoclonic ( sudden spasm of muscles ) jerks → generalized tonic clonic seizure without loss of consciousness Precipitated by sleep deprivation West’s syndrome (infantile spasms) Triad: 1. infantile spasms 2. arrest of psychomotor development 3. hypsarrhythmia Spasms may be flexor, extensor, lightning, nods, usually mixed. Peak onset 4-7 months, always before 1 year. Lennox-Gastaut syndrome Characterized by seizure, mental retardation and psychomotor slowing Three main type: 1. tonic 2. atonic 3. atypical absence Landau- Kleffner syndrome ( acquired aphasia ) Diagnosis in epilepsy Aims: Differentiate between events mimicking epileptic seizures E.g. syncope, vertigo, migraine, psychogenic non-epileptic seizures (PNES) Confirm the diagnosis of seizure (or possibly associated syndrome) and the underlying etiology Diagnosis in epilepsy Approach: History (from patient and witness) Physical examination Investigations History Event Localization Temporal relationship Factors Nature Associated features Past medical history Developmental history Drug and immunization history Family history Social history Physical Examination General esp. syndromal or non-syndromal dysmorphic features, neurocutaneous features Neurological Other E.g. system as indicated Febrile convulsion, infantile spasm Investigations I. Exclusion of differentials: Bedside: urinalysis Haematological: CBP Biochemical: U&Es, Calcium, glucose, ABGs Radiological: CXR, CT head Toxicological: screen Microbiological: LP (Always used with justification) Investigations II. Confirmation of epilepsy: Dynamic investigations : result changes with attacks E.g. EEG Static investigations : result same between and during attacks E.g. Brain scan Electroencephalography (EEG) EEG indicated whenever epilepsy suspected Uses of EEG in epilepsy Diagnostic: support diagnosis, classify seizure, localize focus, quantify Prognostic: adjust anti-epileptic treatment International 10-20 System of Electrode Placement in EEG Electroencephalography (EEG) EEG interpretation in epilepsy Hemispheric or lobar asymmetries Periodic (regular, recurring) Background activity: Slow or fast Focal or generalized Paroxysmal activity: Epileptiform features – spikes, sharp waves Interictal or ictal Spontaneous or triggered Electroencephalography (EEG) Certain epilepsy syndromes have characteristic or suggestive features E.g. Infantile spasms Hypsarrhythmia Childhood absence epilepsy Generalized 3-Hz spike-wave Juvenile myoclonic epilepsy Generalized/ multifocal 4-5 Hz spikewave and polyphasic-wave Benign occipital epilepsy Unilateral/ bilateral occipital sharp/ sharp-slow activity that attenuates on eye opening Lennox-Gastaut syndrome Generalized/ bianterior spike-wave activity at <2.5 Hz Electroencephalography (EEG) E.g. Brief absence seizure in an 18-year-old patient with primary generalized epilepsy Electroencephalography (EEG) Note: Normal in 10-20% of epileptic patients Background slowed by: AED, diffuse cerebral process, postictal state Artifact from: Eye rolling, tremor, other movement, electrodes Interpreted seizure in the light of proximity to Neuroimaging Structural neuroimaging Functional neuroimaging Structural Neuroimaging Who should have a structural neuroimaging? Status epilepticus or acute, severe epilepsy Develop seizures when > 20 years old Focal epilepsy (unless typical of benign focal epilepsy syndrome) Refractory epilepsy Evidence of neurocutaneous syndrome Structural Neuroimaging Modalities available: Magnetic Resonance Imaging (MRI) Computerized Tomography (CT) What sort of structural scan? MRI better than CT CT usually adequate if to exclude large tumor MRI not involve ionizing radiation I.e. not affect fetus in pregnant women (but nevertheless avoided if possible) Functional Neuroimaging Principles When in diagnosis of epilepsy: a region of brain generates seizure, its regional blood flow, metabolic rate and glucose utilization increase After seizure, there is a decline to below the level of other brain regions throughout the interictal period Functional Neuroimaging Modalities available: Positron Emission Tomography (PET) Single Photon Emission Computerized Tomography (SPECT) Functional Magnetic Resonance Imaging (fMRI) Mostly used in: Planning epilepsy surgery Identifying epileptogenic region Localizing brain function Venn Diagram Seizure Therapy Seizure Specific Treatments Anticonvulsant Surgery General Treatment Reassurance and Education Education & Support Information leaflets and information about support group Avoidance of hazardous physical activities Management of prolonged fits Recovery position Rectal diazepam Side effects of anticonvulsants Anticonvulsants Suppress repetitive action potentials in epileptic foci in the brain Sodium channel blockade GABA-related targets Calcium channel blockade Others: neuronal membrane hyperpolarisation Anticonvulsants Drugs used in seizure disorders Tonic-clonic and partial Cabamazepine Phenytoin Valproic acid Absence seizures Ethosuximide Valproic acid Clonazepam Myoclonic seizures Valproic acid Clonazepam Status Epilepticus Short term control Diazepam Lorazepam Infantile Spasms Prolonged therapy Phenytoin Phenobarbital Corticotropin Corticosteroids Adverse Effects Teratogenicity Neural tube defects Fetal hydantoin syndrome Overdosage toxicity Life-threatening toxicity Hepatotoxicity Stevens-Johnson Abrupt withdrawal syndrome Medical Intractability No known universal definition Risk factors High seizure frequency Early seizure onset Organic brain damage Established Operability after adequate drug trials Surgery Curative Catastrophic unilateral or secondary generalised epilepsies of infants and young children Sturge-Weber syndrome Large unilateral developmental abnormalities Palliative Vagal nerve stimulation Surgical Outcome Medical Intractability A well-localised epileptogenic zone EEG, Low MRI risk of new post-operative deficits References 1. 2. 3. 4. 5. 6. Stedman’s Medical Dictionary. MDConsult: Nelson’s textbook. Illustrated Textbook of Pediatrics. Video atlas of epileptic seizures – Classical examples, International League against epilepsy. Guberman AH, Bruni J, 1999, Essentials of Clinical Epilepsy, 2nd edn. Butterworth Heinemann. Manford M, 2003, Practical Guide to Epilepsy, Butterworth Heinemann.
