Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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March 12, 2020
Hypoglycemic Encephalopathy
- Background:
- Hypoglycemia and severe hypoglycemia are defined as plasma glucose levels of 70 mg/dL (3.9 mmol/L) and 40 mg/dL (2.2 mmol/L), respectively.
- It is more common in patients with diabetes, usually occurring as a complication of therapy with insulin or long-acting sulfonylurea drugs. Other causes are insulin-secreting tumors, sepsis, and hepatic or renal failure.
- This patient had recurrent episodes of hypoglycemia secondary to the use of a long-acting oral hypoglycemic agent.
- Clinical Presentation:
- Autonomic: sweating, trembling, palpitations, and anxiety
- Neuroglycopenic: weakness, confusion, personality changes, seizures, and transient memory loss
- In general, autonomic symptoms usually develop before neuroglycopenic symptoms. Severe hypoglycemia may present with altered mental state or coma. Hemiparesis or quadriparesis in patients mimics a stroke.
- Key Diagnostic Features:
- MRI, especially DWI, is the best modality for early diagnosis of hypoglycemic encephalopathy.
- Three distinct imaging patterns are described: 1) predominant gray matter involvement affecting the cortex, neostriatum, and hippocampi; 2) predominant white matter involvement affecting the periventricular white matter, internal capsule, and splenium of the corpus callosum; and 3) a mixed pattern involving both the gray matter and white matter.
- The diffusion changes depend on the severity and duration of hypoglycemia and represent cytotoxic injury, which may be reversible on rapid correction of hypoglycemia. The DWI changes are usually bilateral; however, asymmetric and unilateral changes are also described.
- Asymmetric DWI changes in hypoglycemia are related to regional imbalances between energy supply and demand, spreading depression, or an excitotoxic mechanism.
- The thalamus, brain stem, and cerebellum are generally spared.
- Differential Diagnoses:
- Hypoxic-ischemic brain injury: preceding hypoxic or ischemic event; symmetric globus pallidus or thalamic involvement may help in differentiation
- Creutzfeldt-Jakob disease (CJD): different clinical presentation; characteristic cortical ribbon or hockey stick sign
- Ischemic infarct: follows arterial territory
- Seizure-related changes: may have similar imaging pattern; history and laboratory work-up may help distinguish
- Treatment:
- Prevention of hypoglycemia should be the aim in patients with diabetes mellitus, with an appropriately chosen drug regimen and dietary modifications.
- Mild hypoglycemia is usually managed by oral ingestion of glucose.
- Moderate to severe hypoglycemia is managed by immediate intravenous injection of 25% dextrose or intramuscular glucagon.
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