Differential Diagnosis for Unilateral Neurological Deficits

Single Most Likely Diagnosis

• Acute Transverse Myelitis (ATM): Given the rapid progression of symptoms, including unilateral weakness, pain, and sensation deficits in both the left upper and lower extremities, ATM is a strong consideration. The sparing of the sole of the foot and the involvement of the posterior scapular region also suggest a spinal cord lesion.

Other Likely Diagnoses

• Multiple Sclerosis (MS): The presentation of unilateral neurological deficits, particularly with sensory symptoms and weakness, could be indicative of a relapsing-remitting form of MS, especially given the young age of the patient.
• Spinal Cord Infarction: Although less common, spinal cord infarction could present with acute onset of unilateral or bilateral neurological deficits, including pain, weakness, and sensory disturbances.
• Radiculopathy or Plexopathy: Given the distribution of symptoms, a lesion affecting the nerve roots (radiculopathy) or the brachial plexus (plexopathy) could be considered, especially if there's a history of trauma or compression.

Do Not Miss Diagnoses

• Spinal Epidural Abscess or Hematoma: These conditions are medical emergencies that can present with acute neurological deficits and require immediate intervention to prevent permanent damage or death.
• Spinal Cord Tumor: Although less likely, a spinal cord tumor could present with gradual or acute neurological deficits, depending on the rate of growth and location.
• Vascular Malformations (e.g., AVM): Vascular malformations in the spinal cord could lead to acute neurological deficits due to hemorrhage or ischemia.

Rare Diagnoses

• Sjögren's Syndrome with Neuropathy: This autoimmune disorder can rarely present with neurological manifestations, including neuropathy and myelopathy.
• Neurosarcoidosis: Sarcoidosis affecting the nervous system can present with a wide range of neurological symptoms, including myelopathy.
• Infectious Myelitis (e.g., due to HIV, Lyme, or Syphilis): Certain infections can cause myelitis, presenting with acute neurological deficits, and are important to consider, especially in patients with risk factors.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and diagnostic tests to determine the most appropriate diagnosis and treatment plan.