Encephalopathy refers to altered mental status that includes “disorientation, short-term memory impairment, inattentiveness and abnormal state of arousal. The common causes of encephalopathy are systemic or central nervous system infection, trauma, toxin exposure, metabolic disorders, organ failure, anoxia, endocrine dysfunction, nutritional deficiencies and neoplasms.

Symptoms

Acute encephalopathy is characterized by altered level of consciousness, behavioural changes with or without seizures. When central nervous system infection, inflammation or structural brain disease are excluded. Clinical state of global cerebral dysfunction induced by systemic stress varying in clinical presentation from mild executive dysfunction to deep coma.

Causes

The metabolic encephalopathies could result from lack of glucose, oxygen and vitamin cofactors and organ failure such as hepatic or uremic encephalopathy. Electrolyte disturbances: hyponatremia(low sodium), hypernatremia, hypocalcemia, hypercalcemia, hypophosphatemia, hypomagnesemia, hypermagnesemia e.g Hyponatremia contributes to hypo osmolar stress that drives water into the intracellular space by osmotic forces thereby resulting in cerebral edema.

• Inborn errors of metabolism: Organic acidaemia, urea cycle disorders, mitochondrial cytopathy, Reye syndrome is an acute non-inflammatory encephalopathy that typically manifests with vomiting, lethargy and progression to coma.
• Organ failures: Hepatic encephalopathy, uremic encephalopathy, hypoxic and hypercapnic encephalopathy
• Endocrine causes: Hypoglycaemia, diabetic ketoacidosis, adrenal crisis, hypothyroidism, hyperthyroidism. Hypoglycaemia may occur due to low birth weight, sepsis, hyperinsulinism, inborn errors of metabolism, growth hormone deficiency, adrenal insufficiency and medications
• Nutritional deficiency: Wernicke encephalopathy results from thiamine deficiency and though common in alcoholic patients, it has been reported in infants born to thiamine deficient mother. Children with nutritional deficiencies of vitamins such as thiamine, vitamin B12, folic acid and niacin would manifest with altered level of consciousness, memory disturbances, seizures, ataxia and involuntary movements
• Posterior Reversible Encephalopathy Syndrome (PRES)

Laboratory diagnosis

The aetiology could be established by thorough history taking, clinical examination, arterial blood gas analysis, blood biochemistry tests, neuroimaging and electroencephalography (EEG).

Complete blood count, ESR and CRP fasting blood sugar, sodium, potassium, calcium, phosphorus, magnesium, arterial blood gas, lipid profile, uric acid, liver function test, prothrombin time, creatine kinase, Nutrition and metabolic tests: ammonia, lactate, amino acids, acyl carnitine profile, homocysteine, vitamin B12, prolactin. Endocrine tests: Thyroid function tests and thyroid antibodies, serum cortisol Toxin assay: From gastric aspirate, blood and urine. CSF: Cell count, glucose, protein, lactate, amino acid, neurotransmitters, bacterial culture, PCR for viruses. EEG: To identify background activity, focal slowing, epileptiform discharges, triphasic waves, PLEDS and burst suppression pattern Triphasic waves in hepatic encephalopathy FIRDA in hyperglycaemia, hypoglycaemia and hyponatremia . Ultrasound abdomen, ECG, Echocardiography To look for hepatic and cardiac involvement.

Treatment

General measures in patients presenting with metabolic encephalopathies involve the management of airway, breathing and circulation. Maintain correct electrolytes in blood and id there is in balance supplementing is recommended. Antiepileptic medications must be chosen appropriately to achieve seizure freedom. Raised intracranial pressure if identified must be managed appropriately. The management of hepatic encephalopathy involves maintenance of fluid and electrolyte balance and euglycemia. Other measures that target to decrease the blood ammonia levels in children with hepatic encephalopathy are protein restricted diet. Dialysis must be considered in patients with uremic encephalopathy and these patients also require an emergent management of associated dyselectrolytemia. Therapies in children with Reye syndrome are focused to maintain the cerebral perfusion pressure and also includes supportive measures such 10% dextrose infusion, raised ICP management and correction of hyperammonaemia to minimize the neurological sequelae.