A 45-year-old woman is evaluated for numbness and painful tingling of the right hand. The symptoms began 2 months ago and are especially prominent after she plays tennis. On examination, there is diminished sensation in the lateral palm, thenar eminence, and palmar aspect of the first 3Y:z digits of the right hand.

Educational objective: In the forearm, the median nerve courses between the humeral and ulnar heads of the pronator teres muscle and between the flexor digitorum superficialis and flexor digitorum profundus muscles. Compression prior to the takeoff of the palmar branch (eg, between the heads of the pronator teres} results in sensory loss over the lateral palm and palmar aspects of the first 3~ digits.

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A 35-year-old woman, gravida 2 para 1, comes to the office for prenatal evaluation. The patient says she had been using condoms for birth control and unintentionally became pregnant. Her last menstrual period was 2 months ago, and home pregnancy tests are positive. She has not been taking prenatal vitamins. The patient has a healthy, 5-year-old daughter who was born after an uneventful pregnancy. She has a history of rheumatoid arthritis, and her joint symptoms are controlled with methotrexate therapy. The patient has no other medical conditions and takes no other medications. She does not use tobacco, alcohol, or illicit drugs. Vital signs are within normal limits, and physical examination shows no abnormalities. Serum 13-hCG is elevated, and transvaginal ultrasonograehy shows a normal gestational sac and embryo.

Educational objective: Methotrexate and other folic acid antagonists adversely affect rapidly dividing cells (eg, epithelial cells, stem cells, neural tube cells) by limiting the production of precursors essential to DNA synthesis and repair. If used in the first trimester of pregnancy, these drugs can cause major congenital abnormalities (eg, cardiovascular abnormalities, neural tube defects).

A 55-year-old man comes to the office due to intermittent shortness of breath, cough, and chest tightness over the past 3 months. The patient had asthma as a child that improved in adolescence, and he has not required inhalers or steroids since. He feels that his current symptoms are similar to his prior asthma symptoms. The patient was recently diagnosed with essential tremor, which has improved with medical therapy; he has no other chronic medical conditions. He is a lifetime nonsmoker and does not use alcohol or illicit drugs. Blood pressure is 125175 mm Hg, pulse is 58/min, and respirations are 16/min. Physical examination reveals bilateral scattered expiratory wheezes. Heart sounds are normal and there is no extremity edema.

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.