Applied Radiology

Diagnosis

Hereditary hemorrhagic telangiectasia (HHT) manifested by spinal cord hemorrhage

and vascular malformations in the nasal mucosa and brain.

Findings

The lesions in the cervical and thoracic cord are consistent with intramedullary foci of subacute hemorrhage associated with cord edema (figure 1). The left frontal lesion may be a small cavernous hemangioma or what has been called an "indeterminate" cerebrovascular malformation (vide infra) (figure 2). The lesion in the left nasal cavity is consistent with a vascular malformation and is the cause of recurrent epistaxis, the most common clinical manifestation of HHT (figure 3).

Discussion

Hereditary hemorrhagic telangiectasia, also known as Rendu-Osler-Weber disease, is a hereditary disorder characterized by telangiectasias of the skin and mucosa, and vascular malformations in multiple organs. The primary lesion of HHT is the mucocutaneous telangiectasia, a vascular dysplasia typified by dilated and convoluted veins that often connect directly to dilated arterioles.¹ The other prominent vascular lesion in HHT is the arteriovenous fistula or malformation (AVM), which consists of a direct connection between arteries and veins but is much larger than the telangiectasia.¹ HHT is inherited in an autosomal dominant pattern. Recent genetic studies have linked mutations in the endoglin gene, a cell-surface component of the beta transforming growth factor, to be responsible for some familial forms of HHT.² The clinical diagnosis of HHT is based on the presence of any two of the following: recurrent epistaxis, telangiectasias, evidence of familial inheritance, and visceral involvement.

A variety of neurologic manifestations (including headache, transient ischemia, stroke, seizure, intracerebral and subarachnoid hemorrhage, and brain abscess) have been attributed to pulmonary arteriovenous fistula (PAVF), primary AVM in the brain, AVM of the spinal cord, or portosystemic encephalopathy in patients with HHT.³ Any given patient may have one or more of these lesions. A PAVF may result in neurologic symptoms because of vascular shunting, air embolism, paradoxical embolism, or brain abscess. Various cerebral vascular malformations have been described in patients with HHT and include telangiectasia, cavernous hemangioma, pial AVM, saccular aneurysm, and carotid-cavernous fistula.³ Primary cerebral vascular malformations can cause headache, seizures, and stroke after they hemorrhage into the brain or subarachnoid space. Approximately two-thirds of all neurologic manifestations of HHT are attributed to complications of PAVF and one-third are due to cerebral or spinal AVMs.^3,4

Fulbright et al⁵ have reported the prevalence and types of 63 cerebral vascular malformations seen on MR imaging and angiography in 42 patients with HHT. In this series, "indeterminate" cerebral vascular malformations made up 76% of the lesions and are a heterogeneous group of lesions. These malformations are small (5 to 15 mm) ovoid lesions that variably enhance, and may have high, low, or mixed signal intensity on T2-weighted images. Some of these lesions have features of cavernous malformations, but Fulbright and colleagues believe that they represented small AVMs with abnormal arteriovenous architecture characteristic of vascular lesions found in other organs in patients with HHT. The left frontal lobe lesion in our patient is similar to the "indeterminate" vascular malformation described by these authors.

Vascular malformations of the spinal cord are much rarer central nervous system manifestations of HHT. In a review of the neurologic manifestations of HHT, Roman et al³ found only 17 documented cases of vascular malformations of the spinal cord reported in the literature. Using selective spinal cord angiography, Djindjian et al^6,7 found 7 cases of spinal AVM in HHT among 150 medullary angiomas. These lesions were usually found in the dorsal thoracic cord. Transient paresis, sensory disturbances, anal and bladder dysfunction, muscle wasting, and complete paraplegia may result from shunting of blood, ischemia, mass effect, subarachnoid hemorrhage, or thrombosis. The cord lesions in this case lack one of the typical MR imaging findings described for spinal AVMs, since there were no serpiginous intradural vascular flow voids encircling the cord. In the case of a small AVM, the nidus is not usually seen on MR imaging, although the enlarged feeding arteries and draining veins are often evident and diffuse increased signal in the cord on T2-weight-ed images is also common. This latter finding has been attributed to venous hypertension.⁸ We believe that the two intramedullary lesions in this case probably represent minute "indeterminate" vascular malformations, as described by Fulbright et al⁵ in the cerebrum of patients with HHT, or cavernous hemangiomas.

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2. Rius C: Cloning of the promoter region of human endoglin, the target gene for hereditary hemorrhatic telangiectasia type 1. Blood 12:4677-4690, 1998.
3. Roman G, Fisher M, Perl DP, Poser CM: Neurological manifestations of hereditary hemorrhagic telangiectasia (Rend-Osler-Weber Disease): Report of 2 cases and review of the literature. Ann Neurol 4:130-144, 1978.
4. White RI Jr, Lynch-Nyhan A, Terry P, et al: Pulmonary arteriovenous malformations: Techniques and long-term outcome of embolotherapy. Radiology 169:663-669, 1988.
5. Fulbright RK, Chaloupka JC, Putman CM, et al: MR of hereditary hemorrhagic telangiectasia: Prevalence and spectrum of cere-brovascular malformations. Am J Neuroradiol 19:477-488, 1998.
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7. Djindjian R: Angiography of the Spinal Cord. University Park Press; Baltimore, 1970.
8. Friedman DP, Flanders AE,Tartaglino LM: Vascular neoplasms and malformations, ischemia, and hemorrhage affecting the spinal cord: MR imaging and findings. AJR Am J Roentgenol 162:685-692, 1994.