Case report: Plexiform trigeminal neurofibroma

Case report: Plexiform trigeminal neurofibroma

Clinical Radiology (1988) 39, 313--315 Case Report" Plexiform Trigeminal Neurofibroma A. G H O L K A R , J. P. STACK and I. I S H E R W O O D Depart...

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Clinical Radiology (1988) 39, 313--315

Case Report" Plexiform Trigeminal Neurofibroma A. G H O L K A R , J. P. STACK and I. I S H E R W O O D

Department of Diagnostic Radiology, University of Manchester, Stopford Building, Oxford Road, Manchester MI3 9PT zygomatic arch as well as a 2 mm left proptosis. No abnormal neurological signs were found nor were there clinical stigmata of neurofibromatosis. Plain skull radiographs showed both the left infraorbital foramen and superior orbital fissure to be enlarged. Computed tomography (CT) demonstrated an extracranial soft tissue mass extending into the orbit. A partial excision biopsy revealed a neurofibroma with myxomatous degeneration. Two years later the patient complained of left malar pain and developed a left lower motor neurone facial palsy, but she was not reinvestigated until 1986, when she had developed a swelling of the left cheek. Enhanced thin-section transaxial CT scans were made with an IGE 9800 Scanner, and Multiplanar and three-dimensional reformed views were obtained. This study demonstrated an extensive soft tissue tumour involving the left middle cranial fossa, infratemporal fossa and orbit. It appeared to originate extradurally within the skull, probably from the left Gasserian ganglion, eroding the petrous apex and the

Neurofibromas of the trigeminal nerve are uncommon tumours which usually present in patients in the third or fourth decade of life as a localised mass in the posterior or middle cranial fossa. A case is described of a plexiform neurofibroma of this nerve with unusual clinical and radiological features.

CASE REPORT A 28-year-old female patient presented to another hospital in 1981 with a swelling of the left temple. Clinical examination revealed a tender swelling over the lateral aspect of the left orbit above the


(b) Fig. 1 - Computed tomograms of left trigeminal neurofibroma. (a) Coronal reconstruction showing intra- and extracranial component of the neurofibroma. The left lateral ~all of the sphenoidal sinus and the greater wing and pterygoid processes of the sphenoid bone are partly destroyed. (b) Sagittal reconstruclion s~o.~,ing orbital and infratemporal component of the tumour. In the orbit the tumour is seen involving ophthalmic (arrow) and infraorbital nerve. There is expansion of the infraorbital canal and pressure erosion of the posterior wall of the maxillary antrum.



floor of the middle cranial fossa. All three divisions of the trigeminal nerve were involved, the tumour extending anteriorly along the ophthalmic division, through the left cavernous sinus into the orbit, inferiorly into the infratemporal and pterygopalatine fossae and through the infraorbital canal to involve the soft tissues of the cheek (Fig. la, b). Tumour was also identified in the pterygoid fossa, and the left pterygoid processes of the sphenoid bone were eroded, presumably as a result of growth along the palatine nerves. The posterosuperior border of the left maxillary antrum was eroded (Fig. lb). Three-dimensional reformatted views demonstrated the erosion of the petrous apex, middle cranial fossa, orbit and maxilla particularly well (Fig. 2a, b). Magnetic resonance (MR) images were generated with a Picker International 0.26 Tesla superconducting system. Orthogonal plane scans were obtained using spin-echo sequences to produce TI (TR 560/TE 26) and T2 (TR 2000/TE 80) weighted images. Following intravenous injection of the paramagnetic contrast agent gadolinium DTPA, the TI weighted spin-echo sequences were repeated. These






Fig. 3 - M a g n e t i c resonance sequences of left trigeminal neurofibroma. Coronal section SE2000/80 shows the intracranial extent as a well defined high-signal abnormality lying between the cavernous sinus (arrow) and the temporal lobe. An adjacent slice shows the dumb-bell tumour extending through the floor of the middle cranial fossa into the pterygoid region.


images confirmed the intracranial and extracranial extent of the tumour, the intracranial component being more clearly depicted than by CT (Fig. 3). The bulk of the tumour was best seen on the T2 weighted sequences, except in the orbit, where tumour and intraorbital fat had similar high signals. However, using T1 weighted sequences the tumour was clearly differentiated as a low signal structure in the orbit (Fig. 4a). The bulk of the tumour and its relationship to the adjacent soft tissue structures was best defined in the coronal sections, though its extent was more clearly seen in the sagittal sections. Following gadolinium DTPA injection a moderate degree of tumour enhancement was observed, manifested by a change from low to high signal intensity on the T1 weighted sequences. However, the tumour margin became more difficult to appreciate in the orbit and maxillary sinus (Fig. 4b).


(b) Fig. 2 - Computed tom0grams, three-dimensional images. (a) Anterior view demonstrating expansion of the left superior orbital fissure, the infraorbital foramen and erosion of the orbital floor. (b) Axial view of the floor of the cranium showing apical erosion of the petrous bone and excavation of the base of the middle cranial fossa.

Isolated neurofibromas form about 8% of all primary intracranial tumours (Russell and Rubinstein, 1971). Neurofibroma of trigeminal nerves account for only 0.26% of all intracranial tumours and 2.9% of the intracranial neurofibromas (Schisano and Olivecrona, 1960). Of trigeminal neurofibromas 29% arise in the nerve root and present in the posterior cranial fossa as intradural tumours, 46% arise in the Gasserian ganglion and present in the middle cranial fossa as extradural tumours, and 25% arise in one fossa and extend into the other when they may be both intra- and extradural. Various radiological manifestations have been described related to the anatomical extent of the tumour. Plain skull radiographs may at an advanced stage show smooth erosion of the petrous bone (Levinthal and Bentson, 1976). Displacement of the carotid artery by an avascular or hypovascular mass has been revealed by carotid angiography (Levinthal and Bentson, 1976; Taveras and Wood, 1976). Goldberg et al. (1980) described a variety of CT appearances. Trigeminal neurofibromas are usually either iso- or hypodense and enhance vividly, either homogeneously or non-homogeneously after intravenous injection of a contrast medium. Hyperdense tumours also have been described without contrast enhancement (Naidich et al.





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mon in the cranial nerves. Secondly, the tumour failed to show CT enhancement after contrast infusion- a feature contributing to the failure to detect the intracranial extent of the tumour at the initial CT examination. Three dimensional reformatting has been shown previously to complement conventional CT in the presentation of parasellar pathology (Gillespie et al. 1987). Applied to this patient, this technique undoubtedly allowed a more comprehensive understanding of the extent of the bone destruction to be obtained. Magnetic resonance imaging, as a result of improved contrast and direct multiplanar imaging, provided a method of accurately and rapidly Iocalising the tumour without ionising radiation and without the need for reformatting. It was particularly useful in confirming the intracranial extent of the mass, which was almost isodense on CT. However, these advantages were offset by certain limitations notably that cortical bone possesses a very low signal intensity which makes bone destruction, even when extensive, difficult to identify. The use of gadolinium DTPA provided no additional information; indeed, it made assessment of the extent of the tumour in the air sinuses more difficult, due to equal enhancement of adjacent mucosa. Similarly, by increasing the signal intensity the margin of the intraorbital portion of the tumour became more difficult to distinguish from orbital fatty tissue.


(b) Fig. 4 - Magnetic resonance sequences of left trigeminal neurofibroma. (a) Sagittal section SE500/26 shows the plexiform nature and extent of the tumour as a low signal abnormality9 Its relationship to the adjacent soft tissue structures such as the ocular muscles is evident but the low signal emanating from bone prevents local destruction from being identified. (b) After injection of gadolinium DTPA, the signal intensity of both the neurofibroma and the mucosa has increased, making the tumour margin more difficult to delineate in the orbit.

1976; Kendall and Simon, 1977). The case reported here demonstrates several important radiological features, which are unusual. Plexiform tumours are better known to occur in the peripheral nerves, and they are uncom-

Gillespie, JE, Adams, JE & Isherwood, I (1987). Three-dimensional reconstruction of craniofacial deformity using computed tomography. Neuroradiology, 29, 30-35. Goldberg, R, Byrd, S, Winter, J, Takahashi, M & Joyce, P (1980). Varied appearances of trigeminal neuroma on CT. American Journal of Roentgenology, 134, 57-60. ~" Kendall, B & Simon, L (1977). Investigation of patients presenting cerebello-pontine angle syndromes. Neuroradiology, 13, 65-84. Levinthal, R & Bentson, J (1976). Detection of small trigeminal neurinomas. Journal of Neurosurgery, 45, 568-575. Naidich, TP, Lin, JP, Leeds, NE, Kricheff, IJ, George, AE, Chase, NE et al. (1976). Computed tomography in the diagnosis of extraaxial posterior fossa masses. Radiology, 120, 333-339. Russell, DS & Rubinstein, LJ (1971). Pathology of Tumours of the Nervous System, 3rd edn., pp. 284--304. Williams & Wilkins, Baltimore. Schisano, C & Olivecrona, H (1960). Neurinomas of the Gasserian ganglion and trigeminal root. Journal of Neurosurgery, 17, 306-322. Taveras, JM & Wood, EH (1976). Diagnostic Neuroradiology, pp. 167-169. Williams & Wilkins, Baltimore.