Source / episode info

• **Episode:**647
• **Title:**DIP Ep 647: USMLE Free 86 Series 9 (Q77-86, for Step 2/3)
• **Published:**2026-04-12
• Source:Episode page

One-liner

This episode covers a broad range of high-yield topics including the diagnosis and management of oral squamous cell carcinoma; trauma care for splenic lacerations; neurological presentations like optic neuritis in MS; CNS infections (Toxoplasmosis); late complications of myelomeningocele; sympathomimetic toxicity; biostatistical calculation of Number Needed to Treat (NNT); signs/symptoms of pulmonary embolism; and acute surgical management of peritonitis.

High-yield summary

• Oral Cancer: Fixed, non-healing lesions on the lip are highly suspicious for Squamous Cell Carcinoma (SCC). SCC is often found in immunocompromised patients (e.g., HIV).
• Trauma/Spleen: In a hemodynamically stable patient with splenic laceration, conservative management and observation are preferred over immediate splenectomy due to the spleen's robust immune function.
• MS Neurology: Optic neuritis presents as acute, painless, unilateral vision loss. The optic nerve (CN II) is the most commonly affected cranial nerve in Multiple Sclerosis.
• CNS Infection: In an HIV patient with signs of increased intracranial pressure (papilledema, headache, focal deficits), a space-occupying lesion must prompt suspicion for Toxoplasmosis; treatment involves Pyrimethamine and Sulfadiazine.
• Myelomeningocele Complications: Chronic urinary obstruction from neurogenic bladder function in myelomeningocele patients can progress to high pressures in the collecting system, leading to End-Stage Renal Disease (ESRD).
• Toxicology: Sympathomimetic drugs (Cocaine, Methamphetamine) cause a sympathetic storm characterized by severe hypertension, tachycardia, and mydriasis due to excessive adrenergic stimulation.
• Biostatistics: The Number Needed to Treat ({NNT}) is calculated as 1 / {Absolute Risk Reduction} (ARR). A high NNT suggests low clinical significance.

Learning objectives

• Differentiate the clinical presentation of various oral malignancies, specifically SCC vs. other lip lesions.
• Apply appropriate management principles for splenic trauma based on hemodynamic stability.
• Identify the most common cranial nerve affected by demyelination in Multiple Sclerosis and its characteristic signs.
• Recognize the classic triad (headache, papilledema, focal deficits) suggesting CNS space-occupying lesions in HIV patients, and know the treatment for Toxo.