Differentials
Head injury
SIGNS / SYMPTOMS
No specific clinical differentiating features.
History of head injury is frequently obtained, but can be unavailable in someone who is found unresponsive.
INVESTIGATIONS
CT and MRI will reveal various intracranial bleeds that are associated with head injury; concussions have normal imaging findings; diffuse axonal damage can be seen as signal abnormality in MRI images.
Acute bacterial meningitis
SIGNS / SYMPTOMS
Persistent irritability and lethargy, prolonged postictal obtunded consciousness, skin rash, bulging fontanel, and nuchal rigidity.
INVESTIGATIONS
Typical cerebrospinal fluid abnormalities are pleocytosis, elevated protein, low glucose level, and positive culture.
Viral meningitis
SIGNS / SYMPTOMS
Fever, headache, and 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 PCR 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., HSV, varicella).
Ingestion of toxic substances
SIGNS / SYMPTOMS
History of ingestion of ethanol, methanol, ethylene glycol (constituent of automobile antifreeze), or propylene glycol (diluent in many intravenous medications such as lorazepam) is present.
INVESTIGATIONS
Serum toxicology screen will identify the ingested substance.
Acetaminophen overdose
SIGNS / SYMPTOMS
History of chronic acetaminophen ingestion or acetaminophen overdose is present.
Clinical signs include confusion, tinnitus, hyperventilation, and pulmonary edema.
INVESTIGATIONS
Urine and serum acetaminophen levels will be positive, but not necessarily in the toxic range.
Salicylate poisoning
SIGNS / SYMPTOMS
History of chronic salicylate ingestion or salicylate overdose is present.
INVESTIGATIONS
Serum salicylate levels will be elevated.
Diabetic ketoacidosis
SIGNS / SYMPTOMS
Patients usually have a history of preexisting diabetes mellitus.
May present with polyuria and polydipsia.
INVESTIGATIONS
Plasma glucose >250 mg/dL.
Venous pH <7.3.
HCO₃ <15 mmol/L; anion gap >12.
Presence of serum ketones or beta-hydroxybutyrate.
Urea cycle disorders
SIGNS / SYMPTOMS
History or family history of metabolic defect.
Typically present with recurrent hypoglycemia.
INVESTIGATIONS
Enzyme assay or mutation analysis will be positive for a urea cycle disorder.
Type 1 glycogen storage disease
SIGNS / SYMPTOMS
History or family history of metabolic defect.
Typically present with recurrent hypoglycemia.
May show evidence of growth retardation, with hepatomegaly and protuberant abdomen.
INVESTIGATIONS
Mutation analysis will be positive for GSD I mutations.
Primary carnitine deficiency
SIGNS / SYMPTOMS
History or family history of metabolic defect.
Typically present with recurrent hypoglycemia.
INVESTIGATIONS
Enzyme assay will be positive for a carnitine deficiency.
Fatty acid oxidation disorders
SIGNS / SYMPTOMS
History or family history of metabolic defect.
History or family history of recurrent hypoglycemic episodes.
Frequently presents with lethargy/coma, hepatosplenomegaly.[23] May also present with vomiting, feeding difficulties, cardiomegaly, developmental delay, seizures, ataxia.[19]
INVESTIGATIONS
Plasma and urine analysis of carnitine and acylcarnitine levels reveals disorder.
Additional plasma and fibroblast studies ordered through genetics consultation.
Use of this content is subject to our disclaimer