CASE 7746 Published on 28.08.2009

Extensive neurofibromatosis of the peripheral nerve system. Whole spine plus targeted peripheral MRI.

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Schubert R.
Radiologe am Europa-Center, Berlin, Germany.

Patient

25 years, female

Clinical History
This is a case of a 25 year old woman with known type 1 neurofibromatosis and a painful limb.
Imaging Findings
A 25 year old woman with known neurofibromatosis type 1 was referred for cranial and spinal MRI to assess the disease burden for she exhibited increasing signs of neuropathy on all four extremities. MRI of the right foot was also prescribed because of gait problems and a pain in the right foot on walking. She had some loosely scattered café-au-lait spots and skin nodules at the upper trunk. Apart from that, her outer appearance was normal. Cranial MRI (not shown here) was inconspicuous. There were no bright objects, visual pathway gliomas or skeletal dysplasias. MRI of the whole spine showed extensive bilateral manifestations of neurofibromas in the spinal nerves, the cervicobrachial and lumbar plexus and the Xth cranial nerves (Fig 1-3). Peripheral nerves included in the scan region were also affected. The thoracic spine (not shown) and the whole neuroaxis was spared. MRI of the right foot disclosed the cause of the patient´s gait disturbance: There was a massive atrophy of the foot musculature due to neurofibromas of the distal tibial and fibular nerves and their respective branches (Fig 4).
Discussion
Neurofibromatosis type 1 (NF1) is traditionally classified among a heterogeneous group of hereditary disorders due to primary germ layer abnormalities, the so-called phakomatoses. Common features of all phakomatoses are certain external stigmata, the presence of which can help to determine the diagnosis. However, in times of molecular genetics, this classification is more or less of historical interest.
Type 1 (von Recklinghausen´s disease) is the most common of 3 genetically distinct types of NF, the others being NF type 2 and schwannomatosis. It occurs in about one of 3000 live births. Type 1 has also been termed the peripheral type, for although there may be typical findings in the CNS, the hallmark is a broad spectrum of localised or, more typically disseminated, benign, multinodular, space-occupying lesions of the peripheral nerve system. Non-neurologic manifestations of NF1 are found in the skin, endocrine glands, and the skeletal system. Neurofibromas are peripheral nerve-sheath tumours, what means that they can occur wherever peripheral nerve tissue is present, even in internal organs. Different parts of the nerve sheath may be affected. With respect to surgical treatment, neurofibromas arising from the perineurium will have clean planes of dissection. In contrast, endoneurial and epineurial neurofibromas infiltrate adjacent tissues and are difficult to resect. Infiltrating neurofibromas have also been denoted as plexiform. These are pathognomonic for NF1. Normally, most cases are diagnosed by the age of 10. About 10% present later in life. Family history of the autosomal dominant trait is mostly positive, but up to 50% are due to spontaneous mutations of the NF1 gene on chromosome 17. The mutant gene can be passed on to succeeding generations. Treatment is mainly symptomatic. Debilitating neurofibromas may be treated operatively, but have a strong tendency to recur. Certain neural and extraneural neoplasms have been reported more frequently in NF1 than in patients without the disease. Since the gene product of NF1, neurofibromin, has been isolated and seemingly acts as a tumour suppressor gene, there is hope that genetic engineering will eventually provide a remedy for this disease.
In most requests for diagnostic imaging, the diagnosis of NF1 has already been established. MRI can be useful in equivocal cases and in patients presenting with new or deteriorating symptoms. It can identify dystrophic changes in clinically inconspicuous subjects and has proved useful in the identification of vertebral dysplasia and spinal neoplasms. Low T1 and high T2 signal of neurofibromas is characteristic. After gadolinium administration, the lesions demonstrate confluent or peripheral contrast enhancement in cellular and fibrous elements, whereas myxomatous and cystic regions are comparatively hypovascular.
Whole-body or whole-spine MR examinations have been recommended to assess the extent of the disease. As implied by this report, this approach may not be sufficient. Imaging must be targeted to the signs and symptoms of each individual patient, for these may be caused by the involvement of peripheral nerves not shown on "holistic" imaging.
Differential Diagnosis List
Neurofibromatosis type I (von Recklinghausen´s disease).
Final Diagnosis
Neurofibromatosis type I (von Recklinghausen´s disease).
Case information
URL: https://www.eurorad.org/case/7746
DOI: 10.1594/EURORAD/CASE.7746
ISSN: 1563-4086

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