Multiple Sclerosis (MS): The presence of facial pain, oligoclonal bands in the cerebrospinal fluid (CSF), and white matter changes are highly suggestive of MS, particularly given the subcortical location of the white matter changes. Facial pain can be a presenting symptom of MS, often due to trigeminal neuralgia.

Chronic Migraine or Other Headache Disorders: While the oligoclonal bands point towards an inflammatory or demyelinating condition, facial pain can also be a feature of chronic migraine or other headache disorders. However, the presence of oligoclonal bands would need alternative explanation.
Neuromyelitis Optica Spectrum Disorder (NMOSD): Although less likely than MS given the subcortical white matter changes, NMOSD can present with facial pain and has been associated with oligoclonal bands in some cases. The absence of optic neuritis or spinal cord lesions makes this less likely but does not rule it out.
Systemic Lupus Erythematosus (SLE): SLE can cause a wide range of neurological symptoms, including facial pain and white matter changes on MRI. Oligoclonal bands can also be present in SLE due to its autoimmune nature.

Central Nervous System Lymphoma: Although rare, CNS lymphoma can present with non-specific symptoms including facial pain and white matter changes. The presence of oligoclonal bands could be seen in the context of an immune response to the tumor.
Infectious or Inflammatory Conditions (e.g., Neurosyphilis, Lyme Disease): These conditions can mimic MS or other demyelinating diseases and must be considered, especially if there are atypical features or a lack of response to standard MS treatments.
Vasculitis (e.g., Giant Cell Arteritis): Vasculitis can cause facial pain and neurological symptoms. While oligoclonal bands are not typically a feature, the diagnosis is critical due to the potential for serious complications if left untreated.

Leukodystrophies: A group of rare, genetic disorders that affect the growth or maintenance of the myelin sheath. They can present with white matter changes and a variety of neurological symptoms, including pain.
Mitochondrial Disorders: Conditions like MELAS syndrome can present with a combination of neurological symptoms, including pain, and white matter changes on MRI. Oligoclonal bands might not be a typical feature but could be seen in the context of an inflammatory response.
Susac Syndrome: A rare condition characterized by microangiopathic changes in the brain, retina, and cochlea, leading to a variety of symptoms including headache and white matter lesions. Facial pain could be a part of the headache syndrome.