Differential Diagnosis for Left Facial Numbness

Given a 48-year-old patient with no medical history, a normal neuro exam, and normal CT brain and CT angiography (CTA) of the head and neck, the differential diagnosis for left facial numbness can be categorized as follows:

• Single Most Likely Diagnosis + Trigeminal Neuralgia: This condition is characterized by sudden, severe, shock-like or stabbing pain in parts of the face. However, it can also present with numbness. Given the absence of other findings, this could be a consideration, especially if the numbness is intermittent or accompanied by pain.
• Other Likely Diagnoses + Multiple Sclerosis (MS): Although the patient has a normal neuro exam and imaging, MS can have a varied presentation, and some lesions might not be visible on CT scans. MRI would be more sensitive for detecting MS lesions. + Vitamin Deficiencies (e.g., Vitamin B12): Deficiencies in certain vitamins can lead to neurological symptoms, including numbness. This would be more likely if the patient has a dietary deficiency or malabsorption. + Hypothyroidism: This condition can cause neurological symptoms, including numbness or tingling, although it's less common.
• Do Not Miss Diagnoses + Lyme Disease: If the patient lives in or has visited an area where Lyme disease is common, this should be considered, as it can cause facial numbness among other symptoms. + Sarcoidosis: This autoimmune disease can affect any part of the body, including the nervous system, and cause numbness. + Cancer (e.g., Pancreatic Cancer): Certain cancers can cause facial numbness due to metastasis or paraneoplastic syndromes. Although rare, missing a diagnosis of cancer could be devastating.
• Rare Diagnoses + Sjögren's Syndrome: An autoimmune disorder that can cause neurological symptoms, including numbness, although it's more commonly associated with dry eyes and mouth. + Mitochondrial Myopathies: A group of disorders that affect the mitochondria and can cause a variety of neurological symptoms, including numbness. + Fabry Disease: A genetic disorder that can cause numbness or tingling, among other symptoms, due to the buildup of a particular type of fat in the body's cells.

Each of these diagnoses has a different level of likelihood based on the patient's presentation and the results of the initial diagnostic tests. Further testing, such as MRI of the brain, blood tests for vitamin levels and autoimmune diseases, and possibly a lumbar puncture for MS or infections, would be necessary to narrow down the differential diagnosis.