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Video Report

A case report of pulsating exophthalmos

Debendra Sahu (1), Nick Maycock (1), Adam Booth (2)

1Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK; 2Queen Alexandra Hospital, Southwick Hill Road, Portsmouth PO6 3LY, UK.

Correspondence: Dr Debendra Sahu

Date of acceptance: October 31, 2005

The video is taken of the patients left eye following resolution of the periorbital haematoma. It demonstrates the obvious left pulsatile proptosis.


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History

A 68 year old man presented to the Accident & Emergency Department at our Hospital following a fall from a moped. He was wearing a helmet but the visor had shattered. There was no loss of consciousness but he sustained a dislocated left shoulder and a laceration above the left upper eyelid with a large underlying haematoma.

Following relocation of the left shoulder he was referred for an urgent ophthalmological opinion with regards to a prominent pulsating left exophthalmos.

On examination, his best visual acuities were 6/9 in both eyes. He had a superficial 3cm laceration above the left eye with a large underlying periorbital haematoma and an extensive subconjunctival haemorrhage. He had a pulsating left exophthalmos without an associated bruit. There were no signs of optic nerve dysfunction and the remainder of the ocular examination was unremarkable.

On further questioning the patient stated that the pulsating left exophthalmos had been present for fifteen years. Therefore it was unlikely that this had been caused by an acute traumatic arteriovenous communication which had been suspected on referral. In addition general examination revealed more than six Café au lait macules and several neurofibromas. A tentative diagnosis of NF1 with sphenoid wing dysplasia was made and the patient underwent an outpatient CT and MRI scan of the head.

Figure 1
An axial CT scan of the orbits and brain demonstrates the absence of the left posterior orbital wall which allows the left temporal lobe to bulge forwards into the left orbit.
   
Figure 2
An axial T2 weighted MRI scan of the orbits and brain further demonstrates the herniation of the temporal lobe and the subarachnoid space into the left orbit with close apposition of the orbital and intracranial contents.


Discussion

Neurofibromatosis type1 (NF-1) is one of the most common genetic diseases affecting 1 in 4000 individuals.[1] It is inherited as an autosomal dominant trait and its penetrance is almost complete by five years of age. The NF1 gene responsible for the disease is located on the long arm of chromosome 17 (position17q11.2). It is a large (350kb, 60exons) tumour suppressor gene that codes for the cytoplasmic protein neurofibromin.[2] The deleterious germinal mutations are distributed throughout the entire gene and are generally specific to each family. The frequency of new mutations is unusually high and almost half of the cases are sporadic. NF1 is characterised by a wide variety of clinical expression, even within a given family.[3] The criteria for diagnosing NF1 are well documented1 and not described here in full.

In one subgroup of patients with NF1, cranio - orbital - temporal involvement is the main manifestation of the disorder. Overall, cranio - orbital - temporal neurofibromatosis has been found to exist in 1% to 10% of patients with neurofibromatosis.[4] The principal findings are pulsatile exophthalmos, an enlarged bony orbit, orbital neurofibroma, dysplasia of the sphenoid wing with the presence of herniation of the temporal lobe into the orbit, and a bulging temporal fossa.[4] The resultant gap in the posterosuperior portion of the orbit allows direct contact of the temporal lobe with the orbital soft tissue, simulating an intraorbital space-occupying lesion. The transmitted vascular pulsation of the brain may cause pulsating exophthalmos and can lead to grotesque facial deformity and loss of vision in the affected eye.[5]

The exact mechanism for the sphenoid bone changes seen associated with Neurofibromatosis is uncertain; abnormal skull development, altered transmission of CSF pulsations and interaction between plexiform neurofibroma and sphenoid bone are postulated as possible mechanisms.[6]

Pulsatile proptosis caused by transmitted CSF pulsation can also be caused by large frontal mucocoele, venous angiomas, meningoencephalocoele, lymphangiomas, ruptured orbital cysts and dermoids. These are not associated with a bruit. Pulsatile proptosis caused by arterial pulsation may be associated with a bruit. The two main causes are carotid cavernous fistula or congenital arteriovenous malformation. In our patient the history of longstanding pulsatile proptosis associated with clinical features of NF1 suggested a sphenoid wing abnormality. Further imaging confirmed this diagnosis and ruled out the possibility of a vascular event.


References

    • Neurofibromatosis. Conference statement. National Institutes of Health Consensus Development Conference. Arch Neurol. 1988 May;45(5):575-8.
    • Shen MH, Harper PS, Upadhyaya M. Molecular genetics of neurofibromatosis type 1 (NF1). J Med Genet. 1996 Jan;33(1):2-17.
    • Upadhyaya M, Cooper DN (1998). The mutational spectrum in neurofibromatosis 1 and its underlying mechanisms. Neurofibromatosis type1: from genotype to phenotype.Bios scientific publishers: Pp 65–88.
    • Havlik RJ, Boaz J. Cranio-orbital-temporal neurofibromatosis: are we treating the whole problem? J Craniofac Surg. 1998 Nov; 9(6):529-35.
    • Holt GR. ENT manifestations of von Recklinghausen disease. Laryngoscope, 1978; 88:1617-32.
    • Jacquemin C, Bosley TM, Liu D, Svedberg H, Buhaliqa A. Reassessment of sphenoid dysplasia associated with neurofibromatosis type 1. AJNR Am J Neuroradiol. 2002 Apr;23(4):644-8.