Educational objective: Beta blockers are used in the treatment of essential tremor. Propranolol, a nonselective beta blocker, is the most commonly used therapy and prevents the interaction of epinephrine and norepinephrine with beta-1 and beta-2 receptors to relieve tremor symptoms. However, inhibition of pulmonary beta-2 receptors in patients with underlying reactive airway disease can cause bronchoconstriction, leading to cough, wheeze, and dyspnea.

A 28-year-old woman with a history of type 1 diabetes mellitus comes to the hospital due to abdominal pain, nausea, and vomiting. She is found to have severe hyperglycemia, high anion gap metabolic acidosis, and an elevated beta-hydroxybutyrate level. While being evaluated in the emergency department, the patient develops involuntary, rhythmic jerking of her right upper extremity that lasts for about a minute. She remains fully alert during and after the event. The patient has never had similar symptoms in the past and has no other medical conditions. Physical examination shows no weakness or sensory loss in the right upper extremity.

Educational objective: Seizures are classified as either focal onset if they originate from a localized region of one cerebral hemisphere or generalized if they involve both hemispheres at onset. Focal seizures can be subclassified as retained awareness (patients remain interactive) or impaired awareness (patients appear awake but do not interact appropriately). Manifestations of focal seizure depend on the brain region in which the seizure activity occurs.

A 58-year-old man comes to the emergency department due to sudden right-sided weakness. He has no sensory loss, problems speaking/swallowing, or difficulty with balance. The patient was previously told that he has elevated blood pressure, but he does not routinely follow up with his physician. He takes no medications. Examination shows intact cranial nerves and sensory function. The patient has 3/5 muscle strength on the right side. Initial CT scan without contrast reveals no abnormalities. Four weeks later, repeat brain imaging shows a 9-mm, fluid-filled cavitary lesion in the left internal capsule.

Educational objective: Lacunar infarcts are small, ischemic infarcts (usually <15 mm) involving the deep brain structures (eg, basal ganglia, pons) and subcortical white matter (eg, internal capsule, corona radiata). They most often occur due to hypertension, which causes hardening/thickening of the vessel wall (hypertensive arteriolar sclerosis), predisposing patients with this condition to thrombotic vessel occlusion.

A 40-year-old woman is evaluated for neck pain that has gradually worsened over the past several months. The patient reports a pulling sensation in her neck that causes difficulty in keeping her head straight. She has had no trauma and has no other medical conditions. Physical examination shows a spastic and thickened sternocleidomastoid muscle causing head tilt. The patient is diagnosed with idiopathic torticollis. She is treated with injections of a bacterial product into the affected muscle, with significant relief of her symptoms.

Educational objective: Clostridium botulinum is a spore-forming, gram-positive, anaerobic bacillus that synthesizes botulinum toxin, which prevents the presynaptic release of acetylcholine from the nerve terminal at the neuromuscular junction. Botulinum toxin can be used to treat focal dystonia and other disorders of abnormal muscle contraction.

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.

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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.