A 78-year-old woman is brought to the hospital due to a 2-day history of confusion and involuntary jerking of the upper extremities. Medical history is significant for heart failure with preserved ejection fraction, type 2 diabetes mellitus, and peripheral neuropathy. Her furosemide and lisinopril dosages were increased 3 weeks ago. Other medications include gabapentin, insulin lispro and glargine, and atorvastatin. Vital signs are normal. Examination shows a slightly confused woman with prominent upper extremity myoclonus and dry mucous membranes. The rest of the physical examination shows no abnormalities. Laboratory results are as follows: Furosemide and lisinopril are held. What is the most appropriate next step in management of this patient's myoclonus?

Question

A 78-year-old woman is brought to the hospital due to a 2-day history of confusion and involuntary jerking of the upper extremities.  Medical history is significant for heart failure with preserved ejection fraction, type 2 diabetes mellitus, and peripheral neuropathy.  Her furosemide and lisinopril dosages were increased 3 weeks ago.  Other medications include gabapentin, insulin lispro and glargine, and atorvastatin.  Vital signs are normal.  Examination shows a slightly confused woman with prominent upper extremity myoclonus and dry mucous membranes.  The rest of the physical examination shows no abnormalities.  Laboratory results are as follows: Furosemide and lisinopril are held.  What is the most appropriate next step in management of this patient's myoclonus?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d4d7_01cc_bc81_29899073dafd_MD0003_00 This patient is being evaluated for new-onset encephalopathy (ie, confusion) and upper extremity myoclonus (ie, involuntary jerking). Myoclonus can be due to a variety of causes, including the following: Physiologic (eg, sleep transitions, hiccups) Infectious or metabolic abnormalities (eg, meningitis, liver failure) Neurodegenerative disease (eg, Parkinson, Creutzfeldt-Jakob) Seizure disorder Medication adverse effects (eg, serotonergics, anticonvulsants) To avoid delays in patient care and unnecessary diagnostic testing, a review of medications can promptly identify possible medication-induced myoclonus, which typically resolves after discontinuation. Gabapentin, an analogue of the neurotransmitter gamma-aminobutyric acid, can cause neurotoxicity (eg, myoclonus) in the setting of excessive accumulation in the bloodstream. Gabapentin accumulation often occurs in patients with reduced renal clearance because it is nearly entirely eliminated by the kidneys. This patient with a significant serum creatinine elevation above her baseline, dry mucous membranes, and metabolic alkalosis (suggesting volume contraction) has acute kidney injury (ie, reduced renal clearance) likely due to recently increased diuretic and ACE inhibitor dosages. Patients with chronic kidney disease are also at increased risk if medication dosages are not properly adjusted as renal function declines. (Choices A and E) Once medication-induced myoclonus is excluded, further evaluation for other causes can be pursued based on history and physical examination. In patients with suspected seizures, CNS infection, prion disease, or paraneoplastic syndrome, further testing such as brain imaging, lumbar puncture with cerebrospinal fluid evaluation, and/or electroencephalography can be pursued. (Choice B) Statins (eg, atorvastatin) are not significantly eliminated by the kidneys and therefore do not require cessation or dosage adjustments in patients with reduced renal clearance. Furthermore, statin toxicity causes muscle pain and/or weakness rather than myoclonus and mental status changes. (Choice D) Low serum ferritin (ie, <50 ng/mL) is suggestive of iron deficiency, which is associated with restless legs syndrome (RLS). RLS presents with extremity discomfort during periods of inactivity that creates a voluntary urge to move, rather than the involuntary jerking characteristic of myoclonus. Educational objective: Because of reduced renal clearance, the dosage of medications eliminated by the kidneys (eg, gabapentin) should be decreased or ceased in patients with acute kidney injury and/or chronic kidney disease. Gabapentin toxicity can cause encephalopathy and myoclonus, which typically resolve on discontinuation. References: Gabapentin toxicity in patients with chronic kidney disease: a preventable cause of morbidity. (http://www.ncbi.nlm.nih.gov/pubmed/20362757)

A 78-Year-Old Woman Is Brought to the Hospital Due to a 2-Day