Monument Valley in Arizona

A 34-Year-Old Woman with Diplopia and Left Hemi-Anesthesia

Gregory P. Lekovic, MD, PhD, JD
Robert F. Spetzler, MD
Iman Feiz-Erfan, MD
Nicholas Bambakidis, MD

Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona

Case Presentation

Dr. Lekovic: The patient is a 34-year-old woman who initially presented with complaints of diplopia and left hemibody numbness in 1993 when this lesion was first diagnosed. She subsequently improved symptomatically but suffered recurrent symptoms in 1995, 1997, and 2000. After each event, she recovered well but with increasing residual symptoms. Most recently in December of 2003, she presented again with visual complaints, but they have been improving spontaneously. Her hemibody numbness has resolved completely.

Radiological Diagnosis

Dr. Feiz-Erfan: The patient’s magnetic resonance image shows a heterogeneously enhancing lesion in the dorsal pons and floor of the fourth ventricle (Fig. 1). Evidence of hemosiderin staining on the gradient-echo images is consistent with a cavernous malformation.

Neurosurgical Management

Dr. Lekovic: Would this lesion be a good candidate for a subtonsillar or telovelar approach?

Dr. Spetzler: It is an ideal lesion for the telovelar approach. I would not say subtonsillar, because the point of the telovelar approach is to split the cerebellomedullary fissure just like splitting the Sylvian fissure. This lesion is quite rostral, but it is perfectly accessible using the telovelar approach.

The lesion bulges into the floor of the fourth ventricle, although it does not necessarily reach the surface of the ventricle yet. Moreover, the patient’s symptoms are improving. So at present I would recommend observation. I suspect that the next time this patient hemorrhages the cavernous malformation will reach the surface.

Dr. Bambakidis: Would it be unreasonable to consider a far-lateral or extreme far-lateral approach to this lesion?

Dr.Spetzler: No. Despite what some people may say, it would be feasible to approach this lesion laterally.

Figure 1. Axial T2-weighted magnetic resonance image shows a lesion in the floor of the fourth ventricle.

However, according to the two-point method, one point is placed in the center of the lesion and the other point is placed at
the edge of the lesion where it is nearest the surface. That line is then followed to determine the best angle for the approach. In this case, the telovelar approach would be preferable.

Dr. Lekovic: If the lesion were approached laterally, would an endoscope  be useful?

Dr.Spetzler: No, not really, not in this case. Except as a hand rest.

Given the location of this lesion, we recommend no surgery at this time. If the patient had a persistent medial longitudinal fasciculus (MLF), it would be more tempting to operate. This lesion is surgically resectable, but we would like to see evidence of it symptomatically involving the floor of the fourth ventricle before offering surgery. This will most likely be the case after her next hemorrhage.

Final Diagnosis

Cavernous malformation of the pons.