Clinical approach to optic neuritis: pitfalls, red flags and differential diagnosis.

Demyelinating optic neuritis (ON) is the most common cause of optic neuropathy typically presenting with a subacute painful visual loss. In 20% of patients with multiple sclerosis (MS), ON is the presenting symptom and half of the patients with isolated ON develop MS within 15 years. The diagnosis of ON plays an important role in neurological practice. A correct and early diagnosis is necessary to ensure optimal further investigations and treatment. Other causes of optic neuropathies such as connective tissue disorders, infectious diseases, tumours or ischaemic neuropathies are less frequent but clinical and therapeutic management can differ dramatically. We present five patients admitted to our hospital with suspected demyelinating ON, but the clinical work up revealed different causes of optic neuropathy. We discuss the differential diagnosis of ON and clinical red flags that require careful diagnostic assessment of other diseases. A workflow for the diagnosis of optic neuropathies is presented.