Brainstem Cavernous Angiomas
By Jack Hoch
Brainstem cavernous angiomas have recently received a great deal of attention due to enhanced imaging techniques and the realization that even small hemorrhagic events can cause significant neurological deficits. While the majority (approx. 75%) of cavernous angiomas occur in the upper (“supratentorial”) region of the brain, about 1 in 5 are located in the brainstem or in highly sensitive (“eloquent”), lower (“infratentorial “) areas of the brain.  The most common symptom for brainstem lesions is focal neurological deficit as opposed to seizure or headache for lesions located in surpratentorial regions.
Cavernous angiomas of the brainstem present particular problems to both the affected individual as well as the neurosurgeon. Tightly packed nuclei inhabit the narrow conduit of the brainstem. Any additional mass or introduction of fluid, such as blood products from a bleed, can compress or crush important nerve fibers.  In other words, the smallest of intrusions can result in significant, and potentially life-threatening, symptoms. The nerves that transverse the brainstem control basic, involuntary functions such as respiration, gag reflex, heartbeat regulation, body temperature, pain and heat sensation, and hiccupping as well as other voluntary functions including eye movement, swallowing, facial muscle control, walking, and speech. Both cranial and “long tract” (whole body) nerves can be affected. For the individual, a brainstem cavernous angioma can manifest a disparate range of symptoms making diagnosis difficult. The neurosurgeon must worry about how to manage the case and whether the inherent risks of brainstem surgery are worth the potential beneficial rewards.
While the root cause of a cavernous angioma hemorrhage is not yet understood, there are some consensus guidelines relating specifically to brainstem cavernous angioma case management:
Watch and wait (“conservative” case management). This consists of routine, periodic MRIs to monitor the changes in the lesion. As long as the lesion appears stable and there are no additional symptoms or evidence of hemorrhage, this is usually the most prudent course of action.
Surgical removal (“resection”) may be considered if at least one of the following is true  :
- The lesion abuts the surface of the brainstem that abuts the pia mater, the outer covering of the brain. This type of lesion is called “exophytic”.
- Repeated hemorrhages result in progressively worse deficits
- ·cute hemorrhage is external to the “capsule” of the lesion. In other words, blood from a hemorrhage is entering brain tissue surrounding the cavernous angioma.
- The cavernous angioma has grown to a point where it is pressing upon surrounding brain tissue in a way that causes a visible compression of the surrounding tissue.
One study measured re-hemorrhaging rates as high as 30% per person per year.  Other studies show varying rates of re-bleeding.
Venous anomalies are frequently associated with cavernous angiomas of the brainstem. One study found that all 86 patients met this criterion. It is important to note that any associated venous anomalies should remain undisturbed during surgical resection of cavernous angiomas, as they provide functional drainage.  Elimination of these anomalies can result in infarction and death.
Surgical approaches involving cutting through the floor of the 4 th ventricle should be avoided at all costs.  This does not preclude surgery as an option should the cavernous angioma abut the 4 th ventricle floor; rather, the neurosurgeon must steer clear of approaching the lesion through the floor of this ventricle.
Stereotactic radiosurgery (“gamma knife”) is generally not an accepted method of treatment for brainstem cavernous angiomas.  Relatively high morbidity rates can result, although one study noted reduced hemorrhage rates after radiosurgery.  Unlike radiotherapy for arteriovenous malformations (AVMs), stereotactic radiosurgery does not result in obliteration of the angioma.  At a minimum, radiosurgery treatment for brainstem cavernous angioma is controversial.
Given the advancement in minimally invasive surgical techniques, more and more neurosurgeons are becoming comfortable with surgical removal of cavernous angiomas from the brainstem; however, the potential for significant functional deficits from surgical complications is still significant. This risk must not be taken lightly. The decision to proceed with surgery should be weighed very carefully and implemented only on a case-by-case basis. Assuming one meets the criteria established in part 2 above, one may wish to ask some additional lifestyle questions to help arrive at a decision:
Can I still drive?
Can I work?
Can I take care of the family?
Can I… (whatever else is important in your life)?
Are the symptoms becoming progressively worse?
Am I in decent physical condition to survive the rigors of brain surgery?
Am I young enough such that the odds of having another hemorrhage are greater than if I were much older?
Do I have enough of a support network to help me transcend the potentially arduous recovery process?
Finally, here is a word about diagnostics and imaging. Smaller cavernous angiomas are somewhat difficult to detect. Insist that one of your MRI sequences consists of “gradient-echo” (as opposed to spin-echo or proton beam) imaging. Gradient-echo MRI is most efficient at detecting small, or even punctate (point sized), cavernous angiomas.  Even though a spin-echo MRI may have detected a lesion, it’s always prudent to ensure that there are not additional, smaller lesions which might become a problem later in life.
References  Samii M, Eghbal R, Carvalho GA, Matthies C. Surgical management of brainstem cavernomas.
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