67 Spinal Cord Cavernous Malformations

10.1055/b-0038-162196

67 Spinal Cord Cavernous Malformations

Gursant S. Atwal, Vernard S. Fennell, Leonardo Rangel-Castilla, and Peter Nakaji

Abstract

Cavernous malformations (CMs) of the spinal cord constitute 5 to 12% of all vascular malformations affecting the spine. They commonly involve the dorsal and dorsolateral region of the spinal cord and are more likely to be found in the cervical and thoracic spinal cord. Symptomatic patients present with back pain, sensory, motor, myelopathy, or bowel or bladder symptoms. Typically, the presentation is acute, progressive, and recurrent. CT and MRI are the imaging diagnostic modalities. Microsurgical resection is the treatment of choice for symptomatic patients with spinal cord CM or exophytic large lesions close to or at the pial surface. We manage asymptomatic patients with small lesions asymptomatically, usually less than 3 mm. We offer surgical intervention soon after the onset of symptoms because they exhibit more robust functional improvement than patients whose treatment is delayed. Surgical resection leads to good outcome in most patients. Clinical and radiological long-term follow-up is mandatory in all patients.

Introduction

Vascular malformations of the spine account for a small percentage of spinal pathology. They include capillary telangiectasias, cavernous malformations (CMs), and arteriovenous malformations. These lesions can occur in vertebral bodies, epidural compartments, or intradural compartments, or they can involve the spinal cord itself. In this chapter, we will focus on intramedullary spinal cord CMs.

CMs of the spine are uncommon. They constitute 5 to 12% of the vascular malformations affecting the spine. Most commonly, these CMs are located in vertebral bodies; intramedullary spinal cord CMs are particularly rare. Patient′s age at presentation has been reported in the surgical literature as ranging from 2 to 88 years. There was no correlation with sex in a recent meta-analysis and a slight predominance of males in another.

Major controversies in decision making addressed in this chapter include:

Whether or not treatment is required.
Timing of treatment.
Surgical resection versus radiosurgery.

Whether to Treat

Because of the rarity of these lesions, large prospective natural history studies are lacking in the medical literature. Most of the natural history data come from small series or meta-analyses of several case series.

Patients who present with spinal cord CMs may be symptomatic or asymptomatic ( 1 , 2 in algorithm ). Microsurgical resection is required emergently for symptomatic patients who present with rapid deterioration, whereas it should be done early after diagnosis for those who present with less dramatic deterioration but persistent symptoms ( 3 in algorithm ). Resection is also recommended for asymptomatic patients with large (≥ 3–4 mm) CMs that rise to a pial or an ependymal surface ( 4 in algorithm ).

**Algorithm 67.1** Decision-making algorithm for spinal cord cavernous malformations.

Various series reported an annual hemorrhage rate of 0 to 4.5%. One recent large meta-analysis reported a 2.1% annual hemorrhage rate for these lesions, and another reported 2.5%. Even asymptomatic patients can have evidence of CM enlargement or hemorrhage on magnetic resonance imaging (MRI) ( 5 in algorithm ). However, most natural history data emanate mainly from retrospective studies and therefore should be interpreted with caution because of the inherent limitation of selection bias. Thus, the decision of whether to treat or observe is based on the clinical presentation, severity of symptoms, neurological examination, proximity of the lesion to a pial or an ependymal surface, and the relationship of the lesion with critical spinal cord tracts.

Anatomical Considerations

CMs of the spinal cord most commonly involve the dorsal or dorsolateral region of the spinal cord (▶ Figs. 67.1 and 67.2 ). Ventrally located CMs occur infrequently. CMs in the spinal cord are more likely to be found in the thoracic region.

**Fig. 67.1** Artist′s illustration depicting spinal cord cavernous malformations (CMs). **(a)** Axial image of the spinal cord showing the three possible entry zones for CM resection. **(b)** A midline approach to midline and paramedian spinal cord CMs. **(c)** Dentate ligament is cut on multiple levels to allow spinal cord rotation for a lateral approach to the spinal cord. (Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

**Fig. 67.2** Cervical spinal cord cavernous malformation (CM). A 39-year-old woman presented with subacute history of limb paresthesias and imbalance. Preoperative imaging of the cervical spine demonstrated a large exophytic CM (*arrow*) at the cervicomedullary junction (**a,b**; axial and sagittal magnetic resonance imaging [MRI]). The large exophytic CM could be seen through the exposure (c, intraoperative photograph). The intent was to resect en bloc to develop a plane between the CM and the spinal cord parenchyma, but the lesion was adherent to the spinal cord and had to be removed piecemeal (d, intraoperative photograph). The procedure resulted in complete resection of the CM (e, intraoperative photograph). Postoperative imaging demonstrated complete resection of the CM (f, sagittal MRI). (Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

In addition to having a detailed understanding of the intrinsic spinal cord anatomy and the relationship of the lesion with the tracts, the surgeon must pay close attention to the bony elements. Important considerations are the alignment of the spinal canal and the need for stabilization. Factors that affect stabilization are the amount of bone removal required, the location of the lesion, and the preoperative alignment of the spine.

Pathophysiology

Spinal cord CMs in asymptomatic patients may be discovered incidentally. Evidence of asymptomatic hemorrhages on MRI can lead to their incidental discovery ( 5 in algorithm ). The clinical course and presentation are theorized to be associated with hemorrhages, perilesional gliosis, increase in lesion size leading to local mass effect, and/or local changes in microcirculation secondary to intralesional thrombosis. Because of the small size of the spinal cord and spinal canal, a large hemorrhage may cause a large rapid expansion in the volume within the spinal canal, leading to rapid neurological decline. Chronic progressive myelopathy likely results from small repeated episodes of hemorrhages that cause a hemosiderin-stained gliotic capsule to form adjacent to the spinal cord. The combination of hemorrhage, clot formation, and clot resorption leads to the release of toxic metabolites of hemoglobin, which can cause gliosis, scarring, and destruction of neural tissue. Intramedullary spinal CMs are therefore believed to be more aggressive than their intracranial counterparts.

Workup

Clinical Evaluation

Clinically symptomatic patients may present with pain or sensory, motor, or bowel or bladder symptoms. They may also present with signs and symptoms of myelopathy. The symptomatology of intramedullary spinal CMs may mimic that of demyelinating lesions. When evaluating spinal cord pathology, the surgeon should consider demyelinating lesions and intramedullary tumors in the differential diagnosis.

The clinical course of patients with intramedullary spinal cord CMs has been described as acute, progressive, and recurrent, with varying degrees of improvement. Four different modes of clinical presentation were noted in a series by Ogilvy et al. Discrete acute episodes with progressive neurological deterioration were the most common presentation, followed by progressive neurological decline. Bian et al categorized the clinical course of patients with intramedullary spinal cord CMs as slowly progressive or as a stepwise decline with periods of improvement.

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