Vitamin B12 Deficiency: This condition can cause numbness and tingling in the hands and feet, and sometimes the face, due to demyelination of nerve fibers. A normal MRI would not rule out this diagnosis, as it is a metabolic rather than a structural issue.

Diabetic Neuropathy: Although more commonly associated with distal extremity numbness, diabetic neuropathy can occasionally present with facial numbness. A normal MRI does not exclude this diagnosis.
Hypothyroidism: This condition can cause peripheral neuropathy, leading to numbness in the hands and potentially the face. Thyroid function tests would be necessary to confirm this diagnosis.
Peripheral Neuropathy due to Other Causes: Other causes such as alcohol abuse, certain medications, or autoimmune diseases (e.g., rheumatoid arthritis, lupus) could lead to similar symptoms.

Multiple Sclerosis (MS): Although the MRI is reported as normal, MS can sometimes have a normal MRI early in the disease course, especially if the lesions are not visible or are located in areas not well-visualized by standard MRI sequences. It's crucial to consider MS, especially if other symptoms suggestive of the disease are present.
Cervical Spondylosis with Cord Compression: While a normal MRI might seem to rule this out, the quality of the MRI, the specific sequences used, and the expertise of the interpreter can all influence the detection of subtle cord compression. Clinical correlation and possibly a repeat or more detailed imaging study might be warranted.
Vasculitis (e.g., Giant Cell Arteritis): This condition can cause neurological symptoms, including numbness, due to inflammation of blood vessels. A normal MRI does not exclude vasculitis, and clinical suspicion should prompt further investigation, including blood tests.

Sjögren's Syndrome: An autoimmune disorder that can cause neuropathy, among other symptoms. It's less common but should be considered in the differential, especially if other symptoms of Sjögren's are present.
Neoplastic or Paraneoplastic Syndromes: Rarely, numbness can be a presenting symptom of a neoplasm or a paraneoplastic syndrome affecting the nervous system. A thorough investigation, including screening for underlying cancers, might be necessary in some cases.
Tangier Disease: A rare genetic disorder affecting lipid metabolism, which can lead to neuropathy. It's extremely rare and would be considered only after more common causes have been ruled out.