Schwannomatosis

Schwannomatosis, also known as neurilemmomatosis, is a condition characterised by multiple schwannoma formation but without other criteria to support neurofibromatosis type II (NF2). Some however consider this as a variant of NF2 ¹. 

This article is considering schwannomatosis as an independent disease. 

Epidemiology

It is a rare rare disorder of unknown prevalence. The incidence peak is between between the ages of 30 and 60 years ⁴.

Clinical presentation

Patients frequently present with pain that can can, sometimes, be disabling, resulting in a diminished quality of life.

Diagnostic criteria

• two or more non intradermal (cutaneous) schwannomas

  • at least one with pathological confirmation

• no evidence of any vestibular tumour (it demands high high-quality imaging of the vestibular nerves)

• no known NF-2 mutation
• usually be > 30 years at the time of presentation

Radiographic features

Multiple discrete and well well-defined round lesions round lesions situated along the course of peripheral nerves (peripheral segments of the cranial nerves or paraspinous nerve roots) ⁵.

The majority of patients demonstrate schwannomas confined to one limb or within five or fewer contiguous spinal segments (segmental schwannomatosis) ⁵.

The larger a schwannoma is, the more likely it is to show heterogeneity because of cystic degeneration or haemorrhage. 

CT 

• Schwannomas are usually slightly slightly hypo to to isodense to skeletal muscle with varying degrees of enhancement.
  • small tumours show homogeneous enhancement
  • larger tumours may show heterogeneous enhancement
• adjacent bone remodeling may be seen

MRI

• Typical signal characteristics:
  • T1 - isointense or hypointense
  • T2- hyperintense
  • T1 C+ (Gd) - intense enhancement
• cystic and fatty degeneration are common 
• haemorrhage occurs in 5% of cases 
• calcification is rare
• peripheral arachnoid cysts may be associated

Treatment and prognosis

Symptom control withconsists of pain relief. Asymptomatic Asymptomatic patients are followed and observed.  

When occurs spinalsymptoms of spinal cord compression or symptomsoccur clearly secondary to a schwannoma, surgical intervention is indicated.