Magnetic Resonance Imaging Evaluation of Neurofibromatosis 1 and 2 Manifestations in Iranian Population

Abstract

Introduction: Neurofibromatosis type 1 (NF1) or von Recklinghausen’s disease, is a rare multi-system genetic disorder caused by the mutation of a gene on chromosome 17 which is responsible for synthesis of a protein called neurofibromin and it can cause various neoplasms. Also, Neurofibromatosis type 2 (NF2) is a genetic disorder caused by mutation of Merlin gene, responsible for production of neurofibromin 2 or schwannomin, a cyto-skletal protein. In this study, authors plan to investigate the distribution of these neoplasms and their features on Magnetic Resonance Imaging (MRI). Materials and Methods: From July 2013 to October 2017, we have prospectively enrolled 36 patients with confirmed diagnosis of either NF1 or NF2 based on clinical criteria and post-operative histological examination, to our study and we have performed target-focused imaging, targeting mostly intracranial cavity and spine, and other organs based on patients symptoms to assess the prevalence of neoplasms associated with NF1 and NF2. Also, we have performed specific tests to determine and follow-up the complications of NF1 and NF2, being Electromyography (EMG) and Nerve Conduction Velocity (NCV) for possible spinal cord lesion evaluation and perimetry for evaluation of optic nerve and chiasma lesions in NF1, and audiometry for evaluation of acoustic neuroma and hearing disability in NF2 patients. Results: There were 36 patients, being 20 females and 16 males within 14-40 years old range. NF1 patients comprise 22 cases, being 12 females and 10 males with mean age of 25.7 years and NF2 patients comprise 14 cases, being 9 females and 5 males with mean age of 23.8 years. Perimetry showed affected visual field in 10 patients and neurological examination and EMG-NCV study revealed paresthesia and weakness in upper extremities in 6 patients. Also, audiometry revealed affected hearing pattern in 13 patients. MRI study in NF1 cases revealed Unidentified Bright Objects (UBO) in 15 cases, followed by optic nerve and optic chiasma glioma in 12 cases, spinal cord lesion being as cervical spinal neurofibromas in 6 patients and deep visceral and abdominal plexiform neurofibromas in 4 patients. Moreover, MRI examination in NF2 patients showed bilateral acoustic neuromas in all 14 cases, meningiomas in 9 cases and epenymoma in 2 patients. Also, histopathological examination of removed tissues in surgical candidates or patients with intermediate certainty of diagnosis, confirmed either neurofibromatosis. Conclusion: Although being rare, neurofibromatosis, whether type 1 or type 2, may cause devastating complications and sequel to the affected patients and in some instances; they may manifest themselves as uncommon lesions in neuro-imaging without other visible criteria for the disease. In this study, authors have investigated the possible lesions in association with NF1 and NF2, and incidental finings of these lesions in neuro-imaging or visceral imaging should prompt the suspicion for underlying phakomatosis such as neurofibromatosis.