Seizures - focal
Red flags
- New focal seizure in an adult with no prior epilepsy -> structural lesion until excluded (tumour, stroke, abscess)
- Progressive focal deficit alongside seizures -> mass lesion
- Fever + focal seizure -> encephalitis (especially temporal lobe -> HSV)
- Secondary generalisation to tonic-clonic with prolonged duration -> risk of evolving to status
- New focal seizures with weight loss/known malignancy -> brain metastasis
Differential by mechanism
By localisation (semiology localises)
- Temporal lobe (commonest focal epilepsy) - aura of rising epigastric sensation, deja vu, fear, automatisms (lip smacking, fumbling), impaired awareness
- Frontal lobe - brief, nocturnal, hypermotor/bizarre movements, rapid secondary generalisation, minimal post-ictal confusion
- Occipital - visual phenomena (flashing lights, hallucinations)
- Parietal - sensory symptoms, distorted body image
Aetiology
- Structural: mesial temporal sclerosis, cortical dysplasia, low-grade tumour, prior stroke/trauma, vascular malformation
- Acute symptomatic: acute stroke, encephalitis (classically temporal in HSV), abscess
- Genetic focal epilepsies (less common in adults)
Mimics
- Migraine with aura (typically slower march, longer duration, headache follows)
- TIA (negative symptoms - loss of function - vs seizure's typically positive symptoms)
- Panic attack/dissociative episode
- Transient global amnesia
Focused history
- Detailed semiology - aura, automatisms, motor pattern, level of awareness during the event, post-ictal state, duration
- Progression to secondary generalisation
- Preceding head trauma, CNS infection, febrile seizures in childhood (mesial temporal sclerosis link)
- Known malignancy, immunosuppression
- Triggers, sleep deprivation, medication adherence if known epilepsy
Focused examination
- Full neurological exam for a focal deficit corresponding to seizure semiology (post-ictal Todd's paresis vs persistent lesion)
- Cognitive assessment (temporal lobe epilepsy can affect memory)
- Signs of raised ICP, papilloedema
- Systemic signs of malignancy or infection
Investigation strategy
- MRI brain with epilepsy protocol - superior to CT for structural cause (mesial temporal sclerosis, cortical dysplasia, low-grade tumour); CT first if acute presentation/red flags
- EEG - interictal epileptiform discharges support diagnosis and lateralise/localise
- Bloods as for any new seizure (glucose, electrolytes, LFT)
- LP if febrile/encephalitic features
- Video-EEG monitoring (specialist) if diagnosis or localisation remains uncertain, or for pre-surgical work-up in refractory cases
Management
A. Acute
- Most focal seizures are brief and self-limiting - benzodiazepine only if prolonged (>5 min) or clustering
- Treat any acute symptomatic cause found (e.g. aciclovir if encephalitis suspected, treat stroke)
B. Long-term anticonvulsant choice
- First-line: levetiracetam, lamotrigine, or carbamazepine
- Carbamazepine effective but more drug interactions, hyponatraemia risk, enzyme induction (affects hormonal contraception, warfarin)
- Levetiracetam - favoured for minimal interactions and rapid titration, watch for mood/behavioural side effects
- Same avoid valproate in women of childbearing potential principle as generalised epilepsy
C. Refractory focal epilepsy
- ~30% remain drug-resistant after two adequate trials - refer for epilepsy surgery work-up (video-EEG, MRI, neuropsychology) - mesial temporal sclerosis is the most surgically remediable focal epilepsy
- Vagal nerve stimulation, dietary therapy (ketogenic) as adjuncts if surgery not suitable
D. Underlying lesion
- Treat identified structural cause per its own pathway (tumour resection/oncology referral, stroke secondary prevention)
E. Safety and lifestyle
- Driving restrictions per state law, occupational safety, sleep hygiene, adherence support
Traps
- Mistaking a focal aware seizure for a psychiatric or panic episode because consciousness is preserved
- Not obtaining MRI (relying on CT alone) and missing a subtle structural cause such as mesial temporal sclerosis
- Missing HSV encephalitis in new temporal lobe seizures with fever - treat empirically while awaiting confirmation
- Failing to refer refractory focal epilepsy for surgical work-up after two failed drug trials - delay reduces long-term benefit
- Continuing carbamazepine without checking sodium in a patient with new confusion
Talk track
Semiology localises - temporal lobe (aura, automatisms) is commonest, frontal is brief and nocturnal with rapid generalisation. New focal seizures in an adult need MRI (not just CT) to find the structural cause, especially mesial temporal sclerosis, low-grade tumour, or old injury. First-line drugs are levetiracetam, lamotrigine or carbamazepine; refer for epilepsy surgery work-up after two failed adequate drug trials rather than persisting indefinitely.
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