|LETTER TO THE EDITOR
|Year : 2021 | Volume
| Issue : 1 | Page : 87-88
Plexiform neurofibroma: An uncommon cause of back pain
S Sheetal, Reji Thomas, Aswathy Sasidharan, S Vijayalekshmi
Department of Neurology, Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, India
|Date of Web Publication||27-Apr-2021|
Dr. S Sheetal
16 FG, The Edge, Skyline Apartments, Thirumoolapuram, Thiruvalla - 689 115, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sheetal S, Thomas R, Sasidharan A, Vijayalekshmi S. Plexiform neurofibroma: An uncommon cause of back pain. Indian J Pain 2021;35:87-8
A 23-year-old female presented to us on her 14th postpartum day with complaints of severe low backache with radiation to the left lower limb for the past 3 weeks. Her symptoms started during the last week of her pregnancy. The pain was severe and excruciating and she was unable to even get up and walk due to pain. Pain aggravated with coughing and sneezing and slightest movement of the limb. She did not give history of any weakness, paresthesias, numbness, and bowel or bladder symptoms. On examination, she had a positive straight leg raising test at 20° and mild weakness of the left extensor hallucis longus. No other deficit was noted. Magnetic resonance imaging (MRI) of the lumbosacral spine showed multiple ovoid and elongated lesions, of varying sizes, distributed along the nerve roots of the sacral plexus, located at the level of the neural foramens, with extraforaminal extension, exhibiting T1 isointense and T2/T2 FS/STIR hyperintense signal, suggestive of plexiform neurofibromas [Figure 1]. Neurofibromas appear as high signal intensity on T2-weighted (T2W) images due to increased fluid in myelin associated with dysplastic glial proliferation., Typical target-like appearance on T2W and spectral adiabatic inversion recovery images as central low-signal intensity nerve fascicles and peripheral high-signal intensity of collagenous matrix is also described in plexiform neurofibromas; however it was not seen in our patient. The “fascicular sign” is another radiological sign in neurofibroma, characterised by multiple ring-like structures, which appear as hypointense foci within the hyperintense area on T2W images, possibly reflecting the fascicular bundles seen histologically. Another sign suggestive of neurofibroma is the “split-fat sign.” Neurofibroma in an intermuscular location is usually surrounded by a rim of fat which gives a split fat sign seen on T1W images on MRI. The close differential on imaging is schwannoma; however, they are typically heterogeneously hyperintense on T2 sequences, often with cystic and fatty degeneration. Another differentiating feature is the location of the parent nerve, with respect to the mass; the parent nerve is classically eccentric to the mass in schwannoma but central or obliterated by the mass in neurofibroma. Neurofibromas are common tumors of peripheral nerves and can be found sporadically as solitary tumors unrelated to any apparent syndrome or as part of neurofibromatosis type 1. The term plexiform neurofibroma implies a network-like growth of neurofibroma involving multiple fascicles of a nerve or multiple branches of a large nerve, forming interdigitating network of fingerlike fronds of tumor. Previous reports suggest that plexiform neurofibromas may enlarge in size during pregnancy, probably related to the increased amounts of progesterone and estrogen. Our patient developed symptoms during pregnancy, about one week before delivery. Our patient did not have a positive family history of neurofibromatosis, nor did she have any neurocutaneous markers. Giant plexiform neurofibromas in patients without neurofibromatosis type 1 are quite rare.
|Figure 1: Magnetic resonance imaging of the lumbar spine showing multiple ovoid and elongated lesions, of varying sizes, distributed along the nerve roots of the sacral plexus, located at the level of the neural foramens, with extraforaminal extension, exhibiting hyperintense signal on coronal T2 images (a and b) and isointense signal on coronal T1 fat sat images (c and d)|
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To conclude, giant plexiform neurofibromas are a very rare cause of low backache and they can be present in patients who have no neurocutaneous markers or who are previously undiagnosed with neurofibromatosis type 1. Knowledge about the characteristic radiological features helps the treating physician to consider the differential diagnosis of plexiform neurofibroma, when encountering an infiltrative and branching high-signal intensity lesion, in a patient presenting with severe low backache.
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