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NEURORADIOLOGY Table of Contents   
Year : 2004  |  Volume : 14  |  Issue : 3  |  Page : 317-319
Cranio-orbital-temporal neurofibromatosis : A case report and review of literature


Department of Radiology and Imaging, Command Hospital, Kolkata-27, India

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Keywords: Neurofibromatosis Type 1 (NF-1), pulsatile exopthalmos, sphenoid dysplasia

How to cite this article:
George R A, Godara S C, Som P P. Cranio-orbital-temporal neurofibromatosis : A case report and review of literature. Indian J Radiol Imaging 2004;14:317-9

How to cite this URL:
George R A, Godara S C, Som P P. Cranio-orbital-temporal neurofibromatosis : A case report and review of literature. Indian J Radiol Imaging [serial online] 2004 [cited 2014 Aug 27];14:317-9. Available from: http://www.ijri.org/text.asp?2004/14/3/317/28611

   Introduction Top


Neurofibromatosis is one of the common neuro-cutaneous syndromes (or phakomatoses as they are also referred to as) encountered in clinical practice. The terms "neurocutaneous" and "phakomatosis" both imply that the described condition affects both the skin and central nervous system. Neuroimaging studies are important in evaluation of phakomatoses as most of these diseases reveal prominent and pathognomonic findings. The National Institute of Health (NIH), through its consensus panels, has defined two distinct inherited nerve sheath disorders, Neurofibromatosis Type 1 (NF 1) and Type 2 (NF 2) [1],[2]. The entity of cranio-orbital-temporal neurofibromatosis is an uncommon subtype of NF-1 and is characterized by pulsatile exophthalmos orbital neurofibromas, sphenoid wing dysplasia, expansion of the temporal fossa and herniation of the temporal lobe into the orbit [3]. One such case encountered recently is presented.


   Case Report Top


A 19 year old female patient presented to the Ophthalmology department with proptosis of the left eye of five years duration with minimal progression of the lesion. There was no history of any diminution of vision. Clinical examination revealed the pulsatile proptosis of the Left eye. The visual acuity was normal bilateral, with normal movements of the Left eyeball. No iris nodules (Lisch nodules) were seen. There was a boggy swelling noted over the left upper eyelid on the lateral aspect. On general and systemic examination, no cutaneous nodules, hyper-pigmentation or any skeletal abnormality was detected. No other sibling had similar ailment in the family. A clinical suspicion of carotico-cavernous fistula was made based on the pulsatile proptosis and the patient was sent for neuroimaging.

Axial CT scan of the head [Figure - 1] demonstrated enlargement of the left middle cranial fossa with secondary encroachment on the left orbit. The greater wing of the Sphenoid was seen to be dysplastic and associated with a wide superior orbital fissure. Plain X-ray of the skull PA [Figure - 2] revealed a well-defined region of cranial vault thinning of the left Frontal bone, with the absent innominate line (which is a normal projection of the greater wing of the Sphenoid) in the Left orbit, referred to commonly as the 'bare orbit' sign. T2-weighted sagittal and axial MRI [Figure - 3] and [Figure - 4] demonstrates 'herniation' of the Left Temporal lobe into the posterior aspect of the Left orbit with a preceding anterior sleeve of CSF. Abnormal thickening of the Left upper eyelid produced by a diffuse subcutaneous neurofibroma was seen on T2 -weighted images to be uniformly hyperintense. Enhancement of this skin lesion was seen on post contrast imaging. No optic nerve or orbital tumors were identified. On the imaging findings of dysplastic left greater wing of the Sphenoid and a plexiform neurofibroma of the left upper eyelid, a diagnosis of Neurofibromatosis Type 1 was made.


   Discussion Top


The National Institute of Health (NIH), through its consensus panels, has defined two distinct inherited nerve sheath disorders, Neurofibromatosis type 1 (NF 1) and Neurofibromatosis type 2 (NF 2) [1],[2]. Riccardi [4] suggested as many as eight different subtypes of Neurofibromatosis. NF 1 is far more common than NF 2 and has very prominent clinically evident external lesions. Many of the more common manifestations and diagnostic criteria [1],[2],[5] are summarized in the Table 1: -

NF-1 is an autosomal dominant disorder without racial or sexual predilection, occurring in an estimated 0.05% of the population. Less than half the patients with NF 1 will have a positive family history that suggests a high rate of genetic mutation. Genetic linkage analyses have shown that the gene responsible for NF-1 is on the long arm of chromosome 17 [5]. The normal gene appears to function as a tumor-suppressor oncogene. If both copies of the gene are absent, a variety of neoplasms and non-neoplastic lesions are likely to develop.

NF-1 is an extremely pleomorphic disorder and although attention may dwell on those individuals with classic stigmata who suffer significant morbidity and mortality from symptomatic lesions, many patients are asymptomatic, with few obvious findings and enjoy a normal lifespan. This latter group of patients may not be diagnosed until an autopsy or diagnostic imaging for an unrelated clinical indication reveals the characteristic features.

Review of current literature revealed the entity of cranio-orbital-temporal neurofibromatosis as an uncommon subtype of NF-1, characterized by pulsatile exophthalmos orbital neurofibromas, sphenoid wing dysplasia, expansion of the temporal fossa and herniation of the temporal lobe into the orbit [3], all the features seen in our patient. This entity has not been found reported in the literature in Indian patients till date to the best of our knowledge. The additional feature of thinning of the Left frontal bone seen in our patient has not been described previously.

Proptosis is only occasionally observed in individuals with NF-1 and may result from optic nerve gliomas orbital neurofibromas and rarely due to bone defect at the apex of the orbit [5]. Among the orbital lesions [6] the optic nerve gliomas are the commonest. In addition to the cranial nerves, there are sympathetic, parasympathetic and sensory and motor nerves that traverse the orbit; these may be the source of isolated neurinomas and plexiform neurofibromas.

The isolated variety presents in adulthood with proptosis and is strongly associated with the plexiform type of Neurofibromatosis [7], [8]. Plexiform neurofibromas are poorly defined, crossing fascial planes and surrounding normal structures. Contiguous extension to the face or cranium may be present and is best evaluated by MRI. Signal intensity and enhancement patterns are heterogeneous and variable, as the cellular composition is inconstant [9]. The eyelids are a common site for ocular involvement, as plexiform neurofibromas of the upper eyelid [5].

While the common skeletal lesions include scoliosis, pseudoarthrosis of the long bones, hemihypertrophy, scalloping of the vertebral bodies, internal meningoceles and dysraphic abnormality, Sphenoid dysplasia is one of the "distinctive" bone lesion seen in approximately in 5-10% of NF-1 patients, which is a diagnostic feature using the NIH criteria [1],[2]. The exact mechanism for the sphenoid bone changes seen associated with Neurofibromatosis is uncertain[6]. Abnormal skull development, altered transmission of CSF pulsations and interaction between plexiform neurofibroma and sphenoid bone are postulated as possible mechanisms [7].

The cutaneous manifestations of the diseases are likely to recur and rarely to undergo malignant transformation following surgery[5].Attempts at surgical reconstruction of the sphenoid defect, to separate the orbit from the middle cranial fossa, have met with only limited success due to resorption of bone grafts[3].

 
   References Top

1.Neurofibromatosis. Conference statement. National institutes of Health Consensus Development Conference. Arch Neurol 1998, 45: 575-578.  Back to cited text no. 1    
2.Mulvihill JJ, moderator. Neurofibromatosis 1(Recklinghausen disease) and neurofibromatois2 an update. Ann Intern Med 1990, 113: 39-52.  Back to cited text no. 2    
3.Havlik RJ, Boaz J. Cranio-orbital-temporal neurofibromatosis; are we treating the whole problem? Journal of Craniofacial Surgery 1998, 9(6):529-535  Back to cited text no. 3    
4.Riccardi V. Neurofibromatosis. Phenotype, natural history and pathogenesis, 2nd ed. Baltimore: The Johns Hopkins University Press. 1992.   Back to cited text no. 4    
5.Ebert,EM, Albert DM; The Phakomatoses, in Albertand Jakobiec eds. Principles and practice of Ophthalmology, Philadelphia Pa:WB Saunders Company 2000,Vol 6: 5120-5125  Back to cited text no. 5    
6.Jacquemin C, Bosley TM, Svedberg H; Orbit Deformities in Craniofacial Neurofibromatosis Type 1,Amer J Neurorad 2003; 24: 1678.   Back to cited text no. 6    
7.Jacquemin C, Bosley TM, Liu D. Reassessment of sphenoid dysplasia associated with Neurofibromatosis type 1. Am J Neuroradiology, 2002, Apr;23(4):644-48.  Back to cited text no. 7    
8.Hayman, LA.; Maturi, R.F, Pfleger, MJ. MR imaging of the eyelids: normal and pathologic findings; American Journal of Radiology 1995, 165: 639-644.  Back to cited text no. 8    
9.Imes, RK, Hoyt, WF. Magnetic resonance imaging signs of optic nerve gliomas in neurofibromatosis, American Journal of Ophthalmology 1991, 111: 729-734.   Back to cited text no. 9    

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Correspondence Address:
R A George
Department of Radiology and Imaging, Command Hospital, Kolkata-27
India
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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]

    Tables

[Table - 1]

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