Diagnosed as definite or possible but limited to one limb or ≤5 contiguous segments of spine.Another set of criteria are:

Two or more nonintradermal (cutaneous) schwannomas
No evidence of vestibular tumor
No known NF-2 mutationor

One pathologically confirmed nonvestibular schwannoma plus a first degree relative who meets the above criteria. Treatment
Schwannomatosis patients represent 2.4% to 5% of patients undergoing surgical resection of their schwannomas. In isolated regions of the body schwannomas are small and difficult to locate. Intraoperative sonography offers invaluable assistance in such cases by localizing small schwannomas and decreasing operative time and extent of the surgical incision. If feasible, the schwannomas can be surgically removed. Any tumor-associated pain usually subsides after tumor removal. Damaged nerves and scar tissue can be a result of surgery and pain can be an ongoing problem. Sometimes, a tumor will reappear at the same site after surgery. If surgery is unfeasible, then pain management will have to be used. Schwannomatosis can sometimes cause severe, untreatable pain over time. Other than surgery and/or pain management, there are no other medical treatments available. There are no drugs available to treat Schwannomatosis. Gamma knife radiosurgery can be performed on head tumors to help stop growth of a tumor, although there is no guarantee that it will work. The University of Pittsburgh published their experience with over 829 cases and reported 97% of patients had long term tumor control (defined as requiring no further treatment) with Gamma knife radiosurgery. Recently, many advances are being made in the treatment of schwannomas. Of interest is CyberKnife, manufactured by Accuray.
Another consequence of myelomalacia is improper circulation of blood to the area damaged, resulting in  further damage to the spinal cord. Sport Athletes
Due to extensive physical contact and activity, many athletes become victim to myelomalacia. Any accidents or injuries attained during athletic competition to the spinal cord may result in myelomalacia. Accounts of awkward landing on the ground or being hit intensively have attested to spinal cord injury. Geriatric
With the growth in the elderly population of humans, there has been a rise to myelomalacia. Because the human body begins to deteriorate with age, and because human population is living many years longer, there has been a growth in cases of myelomalacia. As the bones in the body begin to weaken in a process known as osteopenia, the body is more vulnerable to damage. A simple fall may damage the spinal cord and myelomalacia may soon ensue. Diagnosing
There are two tests that can provide a definite diagnosis of myelomalacia; magnetic resonance imaging (MRI), or myelography. Diffuse hyperintensity on T2-weighted imaging, and hypointensity on T1-weighted imaging of the spinal cord can be an indication of the onset or progression of myelomalacia

Treatment
There is no known treatment to reverse nerve damage due to myelomalacia. In some cases, surgery to alleviate the injury to the area may slow or stop further damage. As motor function degenerates, muscle spasticity and atrophy may occur.