A 26-year-old man with a history of excessive daytime sleepiness due to narcolepsy enrolls in a clinical trial evaluating a new stimulant medication. The patient was previously treated with modafinil, but his symptoms did not improve. It is explained to the patient that the new drug works by promoting the release of dopamine and norepinephrine from nerve terminals in the central nervous system. Adverse effects of the drug are due primarily to excess release of norepinephrine from peripheral autonomic nerve terminals.

Educational objective: Primary amebic encephalitis occurs when the free-living, motile protozoan Naegleria fowleri penetrates the olfactory mucosa and migrates in a retrograde fashion through the olfactory nerve to the brain. This rare, deadly infection primarily occurs after exposure to warm, fresh water during recreational activities.

A 65-year-old woman is brought to the emergency department due to abnormal behavior. The patient was in her usual state of health until 3 hours ago, when she suddenly became confused and kept asking repetitive questions. She has had no headache, abnormal motor activity, or focal weakness or numbness. Medical history is significant for hypertension and migraine. Blood pressure is 136/84 mm Hg and pulse is 80/min. On physical examination, the patient is awake and alert but keeps asking, "What happened?" She can state her date of birth and address correctly, recognizes her family members, and is aware of current events. The patient recalls 0 of 3 objects after several minutes and cannot retain the physician's name despite many repetitions. Speech is fluent without dysarthria or aphasia. Cranial nerve examination shows no abnormalities. Motor strength, reflexes, and sensation are normal throughout. Blood cell count and serum chemistry panel are within normal limits. Urine drug screen is negative. CT scan of the head shows no hemorrhage. Two hours later, the patient spontaneously returns to normal.

Educational objective: Meningiomas are common adult intracranial tumors that typically arise in regions of dural reflection (eg, falx cerebri, tentorium cerebelli). Parasagittal lesions compressing the medial portion of the primary somatosensory cortex in the parietal lobe can result in contralateral lower limb sensory loss along with contralateral hemineglect if there is also damage to the parietal association cortex (nondominant hemisphere).

Educational objective: Postherniorrhaphy neuropathy refers to groin pain following hernia repair due to injury involving the cutaneous nerves of the lower abdomen/groin. Neuropathy of the ilioinguinal nerve presents with pain and allodynia in the anterior scrotum (labia majora in women), base of the penis (mons pubis), and medial thigh.