Diagnosis is the process of identifying a particular condition in a systematic way. Differential diagnosis is the method of identifying all possible etiological factors related to all clinical signs and symptoms and then precisely differentiating the diagnosis until an accurate conclusion is reached. Differential diagnosis is essential especially in the field of neurology where many diseases share similar characteristics but do not have a defined neurological examination or test: parkinsonism, migraine, amyotrophic sclerosis and even multiple sclerosis. The differential diagnosis of multiple sclerosis is very broad in nature. About a hundred conditions can mimic multiple sclerosis, this figure is rather underestimated. However, it is impractical and tedious to routinely perform such differential diagnosis to exclude multiple sclerosis. Instead, key characteristics of each patient allow rational consideration of the relevant alternative diagnosis. Potential multiple sclerosis mimics can be easily distinguished from other patients as most patients with relapsing onset present with optic neuritis or myelitis syndromes.1. Monosymptomatic demyelinationIs a single attack of optic neuritis, horizontal myelitis, or any other lesion limited to one anatomical location at a particular time. It represents the first episode of multiple sclerosis. It shares similar symptoms and covers a broad spectrum of other neurological disorders. More than half of cases have an abnormal MRI, with other subclinical lesions elsewhere in the central nervous system. The time factor differentiates this disease from multiple sclerosis. The presence of another lesion after MRI performed one month later will imply multiple sclerosis.2. Schilder's diseaseIt is the demyel...... middle of paper ......d can be increased. Meningeal abnormalities are often visible on MRI. Biopsies of the skin, lungs and lymph nodes are definitive.15. Anterior ischemic optic neuropathy (AION) Is the arrest of the second cranial nerve due to a vascular, vasculitic or atheroclerotic disorder. Subacute or sudden loss of monocular vision may resemble optic neuritis as in multiple sclerosis. The disease commonly affects elderly patients (over 50 years old) with risk factors related to lipid plaques. However, no other symptoms of multiple sclerosis are observed. Normal cerebrospinal fluid and MRI scan are evident.16. Cogan syndromeIt is the disease of interstitial keratitis with deafness and attacks of dizziness. Episodes of ataxia may occasionally occur. Abnormal MRI scans are of rare complaint. Deafness is a very rare incidence in multiple sclerosis. Additionally, cerebrospinal fluid readings are normal.