All of the following statements about extramedullary tumours are true except

Extramedullary intradural spinal tumors are rare. Less than 15% of all central nervous system (CNS) tumors are spinal. Ninety percent of these patients are older than 20 years. Most of spinal tumors are extradural (50-55%) whereas 40-45% are intradural. Fuhermore, 5% are intramedullary and 40% are extramedullary. Most common are Schwannomas (29%), followed by meningiomas (25%) and gliomas (22%). These tumors produce pain syndroms, a variety of neurological symptoms-motor, sensory, sphincter or a combination of thereof. All spinal levels may be involved. The diagnostics includes magnetic resonance imaging (MRI) including contrast enhancement, computerizing tomography (CT) scanning (bone windows with reconstruction) and possibly CT myelograms Presenting signs and symptoms Median time to diagnosis is 12 months and cauda equina location is not presenting earlier than other spinal locations. The symptoms are lesion nonspecific and do not differ between intramedullary and extramedullary locations. Most common initial symptom is pain, which may be local and nocturnal or radiating to arm and/or leg. Sphincter dysfunction, paraparesis and erectile dysfunction occur in 20%, 12% and 2% of patients respectively Ref Harrison20th edition pg 2766