Educational objective: Superior gluteal nerve injury results in weakness and paralysis of the gluteus medius, gluteus minimus, and tensor fasciae latae muscles. This causes the pelvis to tilt downward toward the contralateral side (positive Trendelenburg sign). Patients will also lean toward the ipsilateral side when walking to help stabilize the pelvis (gluteus medius gait).

An 82-year-old man is found unresponsive by his neighbor. The patient lives alone in his suburban home. When the neighbor went to check on him, the patient was on the floor and not answering any questions. His medical history is unknown. On arrival of emergency medical services, the patient is obtunded and responds only to painful stimuli. Supportive measures are begun, including endotracheal intubation, but the patient dies en route to the hospital. Autopsy reveals extensive atherosclerotic disease involving the coronary and internal carotid arteries. Histopathologic examination of the brain in the right middle cerebral artery territory shows neurons with intensely eosinophilic cytoplasm and nuclear fragmentation.

Educational objective: Inadequate blood supply to the brain (eg, arterial thrombosis or embolism) leads to ischemic stroke. The first microscopic changes are typically seen 12-24 hours after irreversible ischemic injury and include intense eosinophilic staining of the neuronal cytoplasm (red neurons) and nuclear fragmentation.

A 32-year-old woman describes five episodes of intractable vomiting over the last year. The episodes last several hours and are associated with a sensation that the room is spinning or tilting. At these times, it is difficult for her to walk because she loses her balance. She cannot relate the timing of the episodes to any particular inciting event. Physical examination reveals stability in the Romberg position and during tandem walk. Proprioception is intact.

Educational Objective: Vertigo is a sensation of excessive motion compared to physical reality. It is most commonly due to dysfunction within the vestibular system.

A 27-year-old woman comes to the office due to severe, unilateral, throbbing headaches that occur several times a month. The headaches are associated with photophobia, nausea, and occasional vomiting. Overthe-counter analgesics do not provide significant symptom relief. Her mother has a history of similar headaches. Vital signs are within normal limits. Physical examination reveals no abnormalities. A medication is prescribed to treat her condition and the patient is instructed to take it immediately at the onset of a headache.

Educational objective: The pathogenesis of migraines is complex and multifactorial but includes neurogenic inflammation, vasodilation, and sensitization of trigeminal afferents in the meninges. Triptans are serotonin 5-hydroxytryptamine 18/1 D agonists that stimulate the trigeminovascular serotonin receptors, resulting in inhibition of vasoactive peptide release, intracranial vasoconstriction, and decreased pain. They are used as abortive therapy for acute migraine.

A Caucasian male who suffers from a severe neurological disease dies of an overwhelming respiratory infection. Autopsy shows an atrophic precentral gyrus and thin anterior roots of the spinal cord. Light microscopy reveals a severe loss of neurons in the anterior horn of the spinal cord and in the hypoglossal and ambiguous cranial nerve nuclei; corticospinal tracts stain only faintly, indicating demyelinization.

Educational objective: Amyotrophic lateral sclerosis (ALS) causes both upper and lower motor neuron lesions. Loss of neurons of the anterior horns of the spinal cord (LMN lesion) causes muscle weakness and atrophy. Demyelination of the lateral corticospinal tract (UMN lesion) leads to spasticity and hyperretlexia.

A 16-year-old girl is brought to the emergency department after she became unresponsive. Temperature is 39.7 C (103.5 F), blood pressure is 70/40 mm Hg, and pulse is 130/min and thready. There is a diffuse petechial and ecchymotic skin rash. Laboratory testing reveals leukocytosis with left shift and evidence of disseminated intravascular coagulation and multiorgan failure. Despite aggressive interventions, the patient dies several hours after admission. Autopsy reveals hemorrhagic necrosis of many internal organs, including the bilateral adrenal glands.

Educational objective: Neisseria meningitidis can cause sepsis and circulatory collapse in previously healthy young individuals. Lipooligosaccharide, a virulence factor in the pathogens outer membrane, is the major underlying cause of disease severity.

An 8-month-old girl is brought to the office for evaluation of irritability and regression of motor skills. Her birth was unremarkable and she appeared to develop normally, but she can no longer sit or roll over. Her parents have also noticed that she startles easily with loud noises. Head circumference measurement is consistent with macrocephaly. Bilateral funduscopic evaluation shows a bright red fovea centralis that is surrounded by a contrasting white macula. Peripheral vision is decreased. Abdominal examination is normal.

Educational objective: Tay-Sachs disease is an autosomal recessive disorder caused by [3-hexosaminidase A deficiency, which results in GM2 ganglioside accumulation. Key clinical features include progressive neurodegeneration and a cherry-red macular spot. In contrast to patients with Niemann-Pick disease, those with Tay Sachs disease have no hepatosplenomegaly.