Differentials
Acute bacterial meningitis
SIGNS / SYMPTOMS
Persistent irritability and lethargy, prolonged postictal obtunded consciousness, skin rash, bulging fontanelle, and nuchal rigidity.
INVESTIGATIONS
Typical cerebrospinal fluid abnormalities are pleocytosis, elevated protein, low glucose level, and positive culture.
Viral meningitis
SIGNS / SYMPTOMS
Fever, headache, neck stiffness are common. Nausea, vomiting, and photophobia can also occur.
INVESTIGATIONS
Cerebrospinal fluid: lymphocytic pleocytosis.
Glucose is normal or high.
Gram stain and bacterial culture are negative; viral culture and polymerase chain reaction may be positive.
Viral encephalitis
SIGNS / SYMPTOMS
Prodromal upper respiratory symptoms with fever and malaise, followed by headache, stiff neck, and seizure.
Skin rash also common.
INVESTIGATIONS
Lumbar puncture may show pleocytosis and increased protein but is sometimes normal.
Culture is negative for bacteria.
Results of viral studies are positive (i.e., herpes simplex, varicella).
Acute encephalopathy
SIGNS / SYMPTOMS
Viral prodrome, vomiting, followed by profound impairment of consciousness and seizures.
Toxins include aspirin (Reye's syndrome).
INVESTIGATIONS
Lumbar puncture may reveal elevated cerebrospinal fluid pressure, increased cell count, and protein, with moderately decreased glucose.
Bacterial cultures are negative.
An elevated cerebrospinal fluid/serum albumin ratio indicates an impaired blood-brain barrier and is the earliest sign of acute viral encephalopathy.[70]
Liver enzymes and blood ammonia may be elevated.
Low blood glucose may be present.
Electroencephalographic abnormalities are variable but are of prognostic significance.
MRI abnormalities may include bilateral thalamic necrosis, white matter lesions, and brain oedema. MRI may also be normal.
Viral studies may be positive (e.g., influenza A).
Epileptic seizure
SIGNS / SYMPTOMS
Afebrile seizure.
INVESTIGATIONS
Electroencephalogram shows paroxysmal epileptiform discharges (e.g., spikes, spike and slow wave).
Generalised epilepsy with febrile seizures plus (GEFS+)
SIGNS / SYMPTOMS
Familial epilepsy syndrome in which patients can have a classic febrile seizure, febrile seizures that persist beyond the age of 5 years (i.e., FS+), and/or epilepsy. Both genetic and environmental factors have been shown to contribute to the pathogenesis of febrile seizure and GEFS+.[71]
Seizures cease by mid-childhood (median age 11 years).
An evolving composite of many syndromes, with shared genetic susceptibility.[72]
INVESTIGATIONS
Genetic tests show links to chromosomes 2q24, 19q13, and 5q31, an autosomal-dominant inheritance with 50% penetrance.
Hot water epilepsy (HWE)
SIGNS / SYMPTOMS
The diagnosis is made by history.
Seizures are usually focal and are precipitated by bathing or pouring hot water (40-50°C [104-122°F]) over the head.
Most common in India and Turkey.
Not age-dependent, but males predominate 3:1. Only 7% have history of febrile seizures.
Family history positive for epilepsy in 22%, and for HWE in 7%.[73]
INVESTIGATIONS
Interictal electroencephalogram shows temporal spikes.
Breath-holding spells
SIGNS / SYMPTOMS
Afebrile infant, with an apnoeic attack, cyanosis, loss of consciousness, and short generalised episodes of jerking of extremities after a crying spell.
The breath is held in expiration.
Onset is 6 to 18 months of age, similar to that of febrile seizures.
Some non-cyanotic, pallid breath-holding spells result from vagal stimulation after an unpleasant, unexpected stimulus.
These are associated with cardiac asystole and are accompanied by syncope or anoxic seizure.
Dravet syndrome: severe myoclonic epilepsy of infancy
SIGNS / SYMPTOMS
Intractable epilepsy, resembling febrile seizure disorder in first year.
Seizure onset early, recurrent (>5), prolonged, often focal and clonic.
There is evidence that vaccination triggers the onset of febrile seizures in one third of patients with Dravet syndrome.[75]
INVESTIGATIONS
SCN1A mutation analysis positive.[76]
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