Arteriovenous malformation with bone lesions

Clinical History

A 32-year-old woman came to the outpatient clinic presenting with a 5-month history of pain in the right ankle. There was not history of trauma. There were not physical examination findings.

Imaging Findings

Ankle radiography showed abnormal cortex of the fibula and tibia, with lytic lesions and cortical thickening; minimal laminar periosteal reaction without fracture and doubtful permeative pattern (Fig. 1).
CT confirmed several cortical lytic punch lesions in the right tibia and fibula, particularly in its lateral side. The permeative pattern was not confirmed. (Fig. 2-4). Associating abnormal soft tissues, with an increased volume of: soleus, flexor hallucis longus, and posterior tibialis, extending to the interosseous membrane, and with fat between the septa (Fig. 5, 6).
RMI showed abnormal vessels in the right leg, from the ankle to the proximal third part of the leg involving posterior calf muscles and extending to the tibiofibular syndesmosis. We also found interosseous drainage vessels causing the cortical punch lesions (erosions) in right tibia and fibula (Fig. 7-14).
The MR dynamic study demonstrated an early arterial mixed component with large drainage veins. Some of these were thrombosed (Fig. 15). There was no evident soft tissue mass.

Discussion

Multiple myeloma is unlikely in this case because of the age of the patient and metastasis as well because an underlying malignancy was ruled out. Therefore the remaining differential diagnosis were: adamantinoma, though this lesion is more likely to be formed in the anterior cortex layer of the tibia; lesions of vascular lineage (haemangioendothelioma and angiosarcoma, vascular malformations) [1] and osteosarcoma, due to the doubtful permeative pattern; and ultimately granulomatous lesions (sarcoidosis and tuberculosis).

The vascular malformations are categorized in two kinds (although there are more classifications): the high flow ones (arteriovenous fistula and arteriovenous malformation (AVM)) and the low flow ones (venous, lymphatic, capillary, capillary-venous…) [1, 2, 3, 4]. This division is based on the dynamic study and is important for surgical planning and it is an image-guidance for therapeutic procedures. The vascular malformations are congenital abnormalities which are present at birth, although they are not always evident. They usually enlarge while the child grows and do not revert [1, 3]. They get exacerbated in puberty, pregnancy, thrombosis, infection or trauma. Unlike haemangioma, vascular malformations may be infiltrative and affect multiple adjacent planes.
The high flow AVM appears clinically as a red, hot, throbbing mass [3]. It can cause an excessive bone growth due to high blood flow. It can also appear as an arterial blood theft or even cortical erosions [2].
The AVM may be complicated by haemorrhage and thrombosis. They are more common in the central nervous system, followed by the head, the neck, the limbs, trunk and viscera [1, 2].
Histopathologically the AVM are dysplastic vessels that connect the veins and arteries forming a nidus.
The RM shows large feeding arteries, serpiginous, with high blood flow and also draining veins, showing a “flow void” in SE sequences and high signal intensity in GRE sequences.
A well-defined mass is absent. Linear septa of fat intensity signal in the lesion are typically observed.
The dynamic study shows arterial, capillary and venous phase images, identifying an early arterial enhancement in case of AVM [1, 3].
The definitive treatment is a transarterial embolization. It is a condition that should be considered in the differential diagnosis of multiple bone lytic lesions [1, 3, 4].
Teaching points:
1. AVM might be associated to bone cortical lesions secondary to enlarge drainage vessels.

Differential Diagnosis List

Final Diagnosis

Arteriovenous malformation

URL:	https://www.eurorad.org/case/13949
DOI:	10.1594/EURORAD/CASE.13949
ISSN:	1563-4086