A mental template for diagnostic medical puzzles: From NEJM Case Records

Most weeks, New England Journal includes a section called Case Records of MGH, a detailed presentation of a puzzling case.  A visiting clinician (who didn't know the patient, only the records) reasons through the case and tries to puzzle it out.

Case 13-2025 has a typical title - "A 70-Year-Old Man with Weight Loss..." but the discussant, MGH's  Matthew Gartland MD, gives us something extra in his discussion and reasoning.  

He shows a four-part framework for putting the numerous puzzle pieces together, which he calls Unboxing, Corners and Edges, Landmarks, and Bridging.   Click on the pic to enlarge:

click to enlarge

Extracts from Discussion - 

Dr. Matthew G. Gartland: This 70-year-old man presented with subacute progressive anorexia, weight loss, and headache. Shortly after admission to this hospital, fulminant encephalopathy developed in the patient.

This case requires iterative clinical reasoning with synthesis of multiple pivot points to arrive at a diagnosis.

The process of clinical reasoning often unfolds much like the way we approach a jigsaw puzzle. Thus, I will apply a framework I will call “jigsaw heuristics” to approach this complex case.

 There are several stages of assembling a jigsaw puzzle, including

·        unboxing the pieces,
·        identifying the corners and edges,
·        assembling landmarks, and
·        bridging across the more homogeneous parts of the puzzle (Figure 2).

·        I will use a similar strategy to develop a differential diagnosis for this patient.

 

 Unboxing

 To start assembling a puzzle, I first empty the box and place all the different pieces right side up. Similarly, in this patient’s case, I begin by laying out the raw data to generate a comprehensive list of problems. The patient’s clinical history is sparse and has several common features, including anorexia, progressive weight loss, and fatigue. Headache and dysgeusia are useful differentiating features, along with abnormalities involving vital signs such as hypertension, findings on physical examination such as scattered bruises and thinning skin, and subsequent laboratory and radiographic findings, including an adrenal nodule, hypokalemia, and hyperglycemia. After he was admitted to this hospital, progressive encephalopathy developed, acute multifocal lacunar infarcts were noted, and the results of CSF analysis were markedly abnormal.

 Corners and Edges

 After unboxing, I often focus on assembling the corners and edges to identify the boundaries of the puzzle. This patient’s presentation contains two discrete timelines that serve as the boundaries of the case, which can be described with time-bound semantic qualifiers. This patient had a subacute-to-chronic syndrome that began at least 6 weeks before hospitalization, with features that include the findings on initial physical examination, such as bruising and thinning skin, as well as the abnormal laboratory test results and radiographic findings on admission. In the hospital, a second process unfolded with fulminant, progressive encephalopathy that may have had a subacute onset. Pertinent findings for this process include intermittent headache, an abnormal CSF profile, multifocal lacunar infarcts, and abnormal results on electroencephalography. At this point, it is unclear where the patient’s weight loss will fit.

 Landmarks

 Once the boundaries of the puzzle are established, we can focus on landmarks by piecing together well-defined shapes. In clinical reasoning, we often search for pivot points — discrete syndromes or findings with a limited differential diagnosis that can be used as a fulcrum for diagnostic thinking.  Potential frameworks around which we can organize our thoughts in this patient’s case include altered mental status, weight loss, and micronutrient deficiency after gastric bypass; however, the patient’s nonspecific clinical presentation lacks differentiating features for these pivot points. We have more pertinent findings that suggest an endocrine disorder, such as Cushing’s syndrome, which would fit within the timeline for a subacute-to-chronic syndrome, followed by encephalopathy with a markedly abnormal CSF profile. These findings are suggestive of a second acute-to-subacute process.

 Bridging

Lastly, I shift to “bridging,” which is the process of methodically completing homogeneous areas of a puzzle by using the shades and shapes of the pieces.

   Cushing’s syndrome…

   Candida meningitis…

   Cryptococcal meningitis…