Background.: Schwannomatosis is a recently recognized form of neurofibromatosis characterized by multiple noncutaneous schwannomas, a histologically benign nerve sheath tumor. As more cases are identified, the reported phenotype continues to expand and evolve. We describe the spectrum of clinical findings in a cohort of patients meeting established criteria for schwannomatosis. Methods.: We retrospectively reviewed the clinical records of patients seen at our institution from 1995–2011 who fulfilled either research or clinical criteria for schwannomatosis. Clinical, radiographic, and pathologic data were extracted with attention to age at onset, location of tumors, ophthalmologic evaluation, family history, and other stigmata of neurofibromatosis 1 (NF1) or NF2. Results.: Eighty-seven patients met the criteria for the study. The most common presentation was pain unassociated with a mass (46%). Seventy-seven of 87 (89%) patients had peripheral schwannomas, 49 of 66 (74%) had spinal schwannomas, seven of 77 (9%) had nonvestibular intracranial schwannomas, and four of 77 (5%) had intracranial meningiomas. Three patients were initially diagnosed with a malignant peripheral nerve sheath tumor; however, following pathologic review, the diagnoses were revised in all three cases. Chronic pain was the most common symptom (68%) and usually persisted despite aggressive surgical and medical management. Other common diagnoses included headaches, depression, and anxiety. Conclusions.: Peripheral and spinal schwannomas are common in schwannomatosis patients. Severe pain is difficult to treat in these patients and often associated with anxiety and depression. These findings support a proactive surveillance plan to identify tumors by magnetic resonance imaging scan in order to optimize surgical treatment and to treat associated pain, anxiety, and depression.

Objectives: Schwannomatosis is a dominantly inherited condition predisposing to schwannomas of mainly spinal and peripheral nerves with some diagnostic overlap with neurofibromatosis-2 (NF2), but the underlying epidemiology is poorly understood. We present the birth incidence and prevalence allowing for overlap with NF2.Methods: Schwannomatosis and NF2 cases were ascertained from the Manchester region of England (population=4.8 million) and from across the UK. Point prevalence and birth incidence were calculated from regional birth statistics. Genetic analysis was also performed on NF2, LZTR1 and SMARCB1 on blood and tumour DNA samples when available.Results: Regional prevalence for schwannomatosis and NF2 were 1 in 126 315 and 50 500, respectively, with calculated birth incidences of 1 in 68 956 and 1 in 27 956. Mosaic NF2 causes a substantial overlap with schwannomatosis resulting in the misdiagnosis of at least 9% of schwannomatosis cases. LZTR1-associated schwannomatosis also causes a small number of cases that are misdiagnosed with NF2 (1%–2%), due to the occurrence of a unilateral vestibular schwannoma. Patients with schwannomatosis had lower numbers of non-vestibular cranial schwannomas, but more peripheral and spinal nerve schwannomas with pain as a predominant presenting symptom. Life expectancy was significantly better in schwannomatosis (mean age at death 76.9) compared with NF2 (mean age at death 66.2; p=0.004).Conclusions: Within the highly ascertained North-West England population, schwannomatosis has less than half the birth incidence and prevalence of NF2.