Differential Diagnosis
- Single most likely diagnosis
- Lung Cancer with Brain Metastasis: The patient's symptoms of cough, weight loss, and recent left-sided weakness with decreased power in the left upper and lower limbs are highly suggestive of lung cancer with metastasis to the brain. The flu-like symptoms could be related to the cancer or a separate infection. Lung cancer is a common cause of weight loss and cough, and brain metastasis can cause focal neurological deficits like the patient's left-sided weakness.
- Other Likely diagnoses
- Tuberculosis (TB): TB can cause chronic cough, weight loss, and fever. It can also affect the brain (tuberculoma) and cause neurological symptoms like weakness. The recent flu-like symptoms could be a separate infection or a manifestation of TB.
- Lymphoma: Lymphoma can cause systemic symptoms like weight loss and fever, and can also involve the lungs and brain, causing cough and neurological deficits.
- Chronic Infections (e.g., Abscess, Empyema): Chronic infections in the lung can cause cough and weight loss, and if they spread to the brain (e.g., brain abscess), can cause focal neurological deficits.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Stroke: Although the patient's symptoms have been progressing over weeks, a stroke (ischemic or hemorrhagic) could cause sudden or gradual onset of focal neurological deficits like left-sided weakness. It's crucial to rule out a stroke, especially given the acute onset of weakness.
- Spinal Cord Compression: This is a medical emergency that can cause progressive weakness, and given the patient's cancer risk factors (e.g., weight loss, cough), it's essential to consider spinal cord compression, especially if there's any back pain or bladder/bowel dysfunction.
- Intracranial Hemorrhage: Similar to stroke, an intracranial hemorrhage could cause sudden onset of focal neurological deficits and is a medical emergency.
- Rare diagnoses
- Paraneoplastic Syndromes: These are rare disorders caused by the immune response to a cancer, but not due to direct local effects of the tumor cells. They can cause a variety of neurological symptoms, including weakness.
- Vasculitis (e.g., Giant Cell Arteritis, Primary Central Nervous System Vasculitis): These conditions can cause a wide range of symptoms, including neurological deficits, and are important to consider, although they are less common.