To the Editor:
We read with great interest the recent article by Mery et al. (3). The authors have presented a well-written and useful technical report, and we agree with their objective presentation, intervention, and conclusion. We also agree with the comments by the reviewing physicians. The report highlights the importance of determining the microsurgical, microvascular anatomy at the time of surgery as well as the importance of the integration of neurodiagnostic results and limitations in formulating a clinical diagnosis and treatment plan.
For example, in the context of nontraumatic subarachnoid hemorrhage of unknown etiology, most neurosurgeons would consider a repeat cerebral panangiogram; however, some research has shown that if the initial angiogram is technically adequate and shows the absence of vasospasm, repeat angiography may have a low yield (1).
When patients present with an incidental aneurysm or a remote history of symptoms, many of these aneurysms frequently are diagnosed on an outpatient basis with the use of magnetic resonance angiography (MRA) without contrast on low-or mid-field MRI machines. Although there are pros and cons regarding the use of open MRI (2), and because there are no Food and Drug Administration-approved MRA contrast agents (4), we have had several patients with anterior and posterior circulation aneurysms who underwent MRA without contrast medium; the MRA procedure was sufficient to determine the dominant feeding vessel and the pertinent preoperative anatomy, such as the direction and 3-dimensional orientation of the aneurysm. Rather than proceeding with contrast, digital subtraction angiography, or angiography, we determined the microsurgical, microvascular anatomy at the time of surgery. These patients had normal outcomes from the surgery without complications.
In the context of hospitalized patients presenting with subarachnoid hemorrhage, we have found 3-dimensional reconstructed computed tomographic angiography useful for preoperative planning. However, after a review of the computed tomographic angiogram by the neuroimaging physician or radiologist and the neurosurgeon, a conventional cerebral angiogram or digital subtraction angiogram is sometimes obtained as well.
Many hospitals lack intraoperative cerebral angiography, digital subtraction angiography, or intraoperative indocyanine green video angiography. In such cases, we have found the low-profile 20-MHz microvascular Doppler probe by Mizuho America, Inc. (Beverly, MA) to be useful. For many elective aneurysm cases, we have found motor-evoked potential monitoring to be useful as well. However, rather than partially incising the aneurysm dome after clipping the neck, we prefer to puncture the dome using a 22-to 25-gauge spinal needle with stylet in place to prevent coring out of the aneurysm wall (similar to the coring that may occur when performing a shunt tap with larger needles without a stylet ). The aneurysm is punctured in a thicker location, usually somewhere between the distal tip and the clip. The stylet is removed, and the aneurysm is aspirated. Obviously, in some cases, the aneurysm may refill and bleed through the small slit-like opening created by the spinal needle and stylet; however, this bleeding can usually be easily controlled. A second clip is applied if possible, and, in some cases, the aneurysm dome may need to be incised to excise atheroma or previously placed coils. We have also routinely continued microscopic observation along with close communication with the anesthesiologist to allow the patient's systolic blood pressure to increase to determine whether there is any change in the presumably secure aneurysm. The microvascular probe has been useful to further assess post-clipping flow through the pertinent microvasculature.
Aneurysms continue to be a technical challenge, and the integration of preoperative, intraoperative, or postoperative neurodiagnostic studies and limitations continue to be problematic. The authors' work highlights the importance of intraoperative neurosurgical microscopic dissection, determination of the pertinent cerebrovascular microanatomy at the time of surgery, and the integration and limitations of neurodiagnostic tools for long-term follow-up of certain cases.
John W. Gilbert
Greg R. Wheeler
Gregory E. Mick
Richard D. Gibbs
1. Gilbert JW, Lee C, Young B: Repeat cerebral pan-angiography in subarachnoid hemorrhage of unknown etiology. Surg Neurol
2. Gilbert JW, Wheeler GR, Lingreen RA, Johnson RR: Open stand-up MRI: A new instrument for positional neuroimaging. J Spinal Disord Tech
3. Mery FJ, Amin-Hanjani S, Charbel FT: Is an angiographically obliterated aneurysm always secure? Neurosurgery
5. Weiser HC, Gilbert JW: Needle size for puncture of a Rickham reservoir. Surg Neurol