Primary CNS lymphoma (PCNSL), a rare form of non-Hodgkin lymphoma that is confined to the brain, is usually of B-cell origin. Primary leptomeningeal lymphoma, regardless of T or B-cell origin, is an unusual site of presentation. Out of 100 consecutive PCNSL patients that we have followed up in our center during the last 10 years, five had T-cell lymphoma (5%). All presented with leptomeningeal involvement as the sole manifestation and four of them presented with neuronal lymphomatosis. Presenting symptoms included signs of elevated intracranial pressure with 6th nerve palsy; headache and bilateral 3rd nerve palsy; mononeuritis multiplex and unilateral hearing loss; bilateral 7th nerve paralysis and bilateral uveitis. Because neither the CSF nor the MRI were indicative, meningeal or nerve biopsies were required for conclusive diagnosis. Four patients died 10-19 months from disease onset and one patient is alive 36 months following the diagnosis. We conclude that T-cell PCNSL can present as an isolated leptomeningeal involvement which may be associated with neurolymphomatosis affecting cranial and peripheral nerves. These manifestations mimic other neurological conditions such as pseudotumor cerebri or vasculitis. Diagnosis is difficult and, as a result, frequently delayed. This calls for early consideration of meningeal or nerve biopsy whenever CSF findings are inconclusive.