Multiple Sclerosis (MS): Although a normal MRI does not rule out MS, especially in its early stages or in cases where lesions are not visible on standard MRI sequences, the presence of elevated oligoclonal bands in the cerebrospinal fluid (CSF) is a hallmark of the disease. MS is characterized by demyelination, inflammation, and axonal degeneration in the central nervous system.

Neurosyphilis: This condition can present with elevated oligoclonal bands due to the inflammatory response within the central nervous system caused by syphilis infection. Neurosyphilis can have a variety of clinical presentations and may not always show characteristic findings on MRI.
Subacute Sclerosing Panencephalitis (SSPE): A rare but serious condition caused by a persistent infection with the measles virus. It leads to inflammation of the brain and can present with elevated oligoclonal bands. MRI findings may be nonspecific or normal in early stages.
Lyme Neuroborreliosis: In some cases, Lyme disease can affect the central nervous system, leading to elevated oligoclonal bands. Early stages or certain forms of the disease might not show significant abnormalities on MRI.

Central Nervous System Lymphoma: Although less common, CNS lymphoma can present with elevated oligoclonal bands and might not always be visible on a standard MRI, especially if the lesions are small or located in areas difficult to assess.
Infectious Encephalitis: Certain viral or bacterial encephalitides can cause an inflammatory response leading to elevated oligoclonal bands. The MRI might appear normal if the infection is in its early stages or if the pathology is not extensive enough to be visualized.
Paraneoplastic Syndromes: These are rare disorders that are triggered by an altered immune system response to a neoplasm. They can affect the central nervous system and lead to elevated oligoclonal bands, with potentially normal or nonspecific findings on MRI.

HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP): A rare condition caused by the human T-lymphotropic virus 1 (HTLV-1), leading to progressive spastic paraparesis and other neurological symptoms. Elevated oligoclonal bands can be present, and MRI findings may be minimal or nonspecific.
Neuromyelitis Optica Spectrum Disorder (NMOSD): An autoimmune inflammatory condition primarily affecting the optic nerve and spinal cord. While it often presents with characteristic lesions on MRI, early or mild cases might have normal imaging, and elevated oligoclonal bands can be present in some cases.
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Although primarily a peripheral nervous system disorder, CIDP can have central nervous system involvement, leading to elevated oligoclonal bands. MRI of the brain might be normal, focusing attention on peripheral nerve and root enhancement.