Chapter 11: Toxic and Metabolic Abnormalities

Toxic-metabolic neurologic conditions result from dysfunction of the central and peripheral nervous systems secondary to systemic processes, derangements of other organ systems, or pathologic accumulation (or absence) of certain substances. This domain of neurology encompasses conditions which may be acquired or genetic, reversible or irreversible, acute or chronic, pediatric-onset or adult-onset. They do not fit neatly into any specific domain of the established neurology subspecialties and thus require all neurologists to have a working familiarity with them. Often, toxic-metabolic effects on the nervous system manifest when patients are admitted to non-neurological inpatient services. Patients with chronic symptoms are also commonly referred to outpatient general neurology clinics. While the term “toxic-metabolic encephalopathy” is a common diagnosis for the consulting neurologist, it is important for readers to recognize the laboratory findings and imaging patterns that correlate with specific diagnoses to optimize treatment recommendations for patients and non-neurologists. The following 8 Teaching NeuroImages span a variety of toxic-metabolic conditions that a neurologist may encounter.