A 65-year-old woman presents to her primary care physician with complaints of new-onset memory loss. Her family reports that she has been forgetting recent events, repeating questions, and misplacing items more frequently over the past few months. She has no significant medical history but has noticed a decline in her cognitive abilities. On examination, she demonstrates difficulty recalling recent events and exhibits word-finding difficulties. Her Mini-Mental State Examination (MMSE) score is 20/30. What is the most likely diagnosis for this patient, and what are the hallmark clinical manifestations? (Select all that apply)

 

Choice A reason: Ventilation-perfusion (V/Q) mismatch, where lung regions receive inadequate ventilation or perfusion, is the most common cause of hypoxemia. Conditions like pneumonia or pulmonary embolism disrupt this balance, reducing oxygen exchange, making this the primary cause in clinical settings.

Choice B reason: Hyperventilation with hypocapnia lowers carbon dioxide but does not typically cause hypoxemia, as oxygen levels are usually maintained or increased. It affects acid-base balance more than oxygenation, making this an incorrect primary cause of low oxygen levels.

Choice C reason: Reduced diffusion distance is not a cause but a facilitator of gas exchange. Impaired diffusion (e.g., pulmonary edema) can contribute to hypoxemia, but V/Q mismatch is more prevalent across conditions, making this less common as a primary cause.

Choice D reason: Shunting, where blood bypasses ventilated alveoli, causes hypoxemia but is less common than V/Q mismatch. It occurs in specific conditions like congenital heart defects or ARDS, but V/Q mismatch predominates in most respiratory disorders, making this incorrect.

Choice A reason: Absence seizures involve brief staring spells, not continuous tonic-clonic movements. The patient’s prolonged, unresponsive seizure activity indicates status epilepticus, so this is incorrect for the seizure type.

Choice B reason: Status epilepticus is continuous or recurrent seizures lasting over 5 minutes, often tonic-clonic, with unresponsiveness, tachycardia, and hypertension. This matches the patient’s presentation, making it the correct type.

Choice C reason: Myoclonic seizures cause brief muscle jerks, not prolonged tonic-clonic activity. Status epilepticus describes the continuous seizure state, so this is incorrect for the observed seizure.

Choice D reason: Tonic-clonic seizure is a single event, but continuous activity suggests status epilepticus. The prolonged duration and unresponsiveness point to status, so this is incorrect.