28 What is encephalopathy? Global brain dysfunction often accompanied by confusion or delirium What are some common examples of mechanisms leading to encephalopathy? • Cerebral edema • Disruption of neurotransmitters • Alteration of membrane excitability secondary to electrolyte abnormalities • Nutritional disorders that lead to cell death • Toxins causing impaired oxygen delivery or mitochondrial dysfunction What are the toxins responsible for encephalopathy in hepatic dysfunction? Ammonia1 and endogenous benzodiazepine-like compounds2 What are the signs and symptoms of hepatic encephalopathy? Mental status changes, signs of cirrhosis, insomnia/hypersomnia, asterixis, bradykinesia, transient decerebrate posturing What is the classic finding on MRI in patients with hepatic encephalopathy? High signal intensity in the globus pallidum on T1-weighted images3 What is the mechanism of this finding? Increased tissue concentrations of manganese leading to dysregulation of cell volume3 What is the common presentation of uremic encephalopathy? Fluctuating periods initially of apathy, fatigue, inattentiveness, and irritability, followed by confusion, dysarthria, tremor, and asterixis, which can lead rarely to psychosis, hallucinations, delusions, or catatonia4 What is the most common finding on EEG in uremic encephalopathy? Prominence of slow waves What toxic substances accumulate in uremic encephalopathy? Many metabolites and compounds accumulate, most notably urea, guanidine compounds, uric acid, hippuric acid, amino acids, polypeptides, and polyamines.5 What syndrome can develop in patients with renal failure or with uremic encephalopathy that is characterized by myoclonic jerks, twitches, or fasciculations? Uremic twitch-convulsive syndrome What syndrome is commonly associated with uremic encephalopathy? Hypertensive encephalopathy What areas of the brain are most commonly affected by hypertensive encephalopathy? Posterior aspects including cerebellum and brainstem What are the radiographic findings of hypertensive encephalopathy? Posterior leukoencephaly6 Why does hypertension lead to destruction of primarily the posterior aspect of the brain? This is due to the paucity of the vascular supply of the posterior circulation of the brain (watershed areas).7 What is the most common electrolyte abnormality in clinical practice? Hyponatremia7 Why are sodium (Na) levels monitored closely in neurosurgical patients? The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a relatively common cause of hyponatremia in the neurosurgical ICU patient, which can quickly lead to cerebral edema and death. Cerebral salt wasting (CSW) is another frequent cause of life-threatening hyponatremia, which requires a different intervention from that for SIADH.8 What is the most likely pathophysiological mechanism behind cerebral salt wasting?
Encephalopathy
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