Differential Diagnosis for Cognitive Impairment

The patient presents with a 6-week history of increasing forgetfulness, difficulty remembering past events, and impaired ability to recall recent information, along with psychomotor retardation, flat affect, and signs of neglect in personal hygiene. These symptoms, combined with her past medical history and laboratory findings, guide the differential diagnosis.

• Single Most Likely Diagnosis

  • Depression with Cognitive Impairment: The patient's history of similar symptoms that were successfully treated with medication, combined with current symptoms of psychomotor retardation, flat affect, difficulty sleeping, decreased appetite, and significant weight loss, strongly suggests a depressive episode. Depression can cause significant cognitive impairment, often referred to as pseudodementia, which presents similarly to dementia but is reversible with treatment of the underlying depression.

• Other Likely Diagnoses

  • Alzheimer's Disease or Other Dementias: Given the patient's age and symptoms of memory loss, difficulty recalling past events, and trouble with sequences, dementia should be considered. However, the presence of significant depressive symptoms and a history of responsive treatment for similar episodes makes this less likely as the primary diagnosis at this time.
  • Chronic Kidney Disease (CKD): The patient's elevated serum creatinine level indicates impaired renal function. CKD can lead to cognitive impairment due to the accumulation of toxins. However, this would not fully explain the patient's psychiatric symptoms and history.
  • Medication Side Effects: Although not specified, the patient may be on medications that could contribute to cognitive impairment. Given her age and potential for polypharmacy, this is a plausible consideration.

• Do Not Miss Diagnoses

  • Hypothyroidism: Can cause cognitive impairment, depression, and weight loss. It's crucial to rule out hypothyroidism due to its potential for significant impact on cognition and mood, and its ease of treatment.
  • Vitamin B12 Deficiency: Can lead to cognitive impairment, depression, and neurological symptoms. Given the patient's weight loss and potential for malnutrition, this is an important diagnosis not to miss.
  • Infections or Sepsis: Although the patient's temperature is normal, underlying infections can sometimes present with non-specific symptoms such as confusion and altered mental status, especially in the elderly.

• Rare Diagnoses

  • Normal Pressure Hydrocephalus (NPH): Presents with the triad of gait disturbance, dementia, and urinary incontinence. While the patient shows some cognitive decline, the full triad is not described, making this a less likely but not impossible diagnosis.
  • Creutzfeldt-Jakob Disease: A rare, degenerative, fatal brain disorder that leads to dementia and other neurological problems. It is characterized by a rapid progression of symptoms, which is not clearly indicated in this scenario.
  • Neurosyphilis: Can cause cognitive decline, personality changes, and psychiatric symptoms. Given the low prevalence and the absence of specific risk factors or symptoms suggestive of syphilis, this is considered rare but should be kept in mind, especially if other diagnoses are ruled out.