This AANS presidential address focuses on enduring values of the neurosurgical profession that transcend the current political climate. The address was delivered by Dr. Batjer during a US presidential election year, but the authors have intentionally avoided discussing the current chaos of the American health care system in the knowledge that many pressing issues will change depending on the outcome of the 2016 elections. Instead, they have chosen to focus on clarifying what neurosurgeons, and the American Association of Neurological Surgeons, in particular, stand for; identifying important challenges to these fundamental principles and values; and proposing specific actions to address these challenges. The authors cite “de-professionalism” and commoditization of medicine as foremost among the threats that confront medicine and surgery today and suggest concrete action that can be taken to reverse these trends as well as steps that can be taken to address other significant challenges. They emphasize the importance of embracing exceptionalism and never compromising the standards that have characterized the profession of neurosurgery since its inception.
H. Hunt Batjer and Vin Shen Ban
Clinical presentation, diagnostic evaluation, and surgical treatment
Hunt Batjer and Duke Samson
✓ Infratentorial arteriovenous malformations (AVM's) represent only 5% to 1% of all AVM's in major series. Since 1977, 32 patients with intracranial intradural malformations of the brain stem or cerebellum have been evaluated at the University of Texas Health Science Center, 30 of whom underwent surgical treatment. Twenty-three patients presented with intracranial hemorrhage, which was recurrent in 11 cases, and nine patients were evaluated for progressive brain-stem or cerebellar deficits. A history of progressive deficits was unusual in the group that presented with hemorrhage, and a prior or subsequent hemorrhage was rare in the patients initially evaluted for progressive deficits. Seventeen of these AVM's were located in the vermis, seven within the cerebellar hemisphere, two in the tonsil, two in the cerebellopontine angle, and four within the brain stem. Operative intervention was directed at primary resection in 15 cases, staged resection in seven, embolization and resection in five, and evacuation of hematoma in three. Operative mortality in this surgical series was 7%, with significant morbidity in 13%. Use of modern microsurgical techniques in removal of posterior fossa AVM's may offer results better than the natural history of the disease process, especially in patients who present with hemorrhage.
H. Hunt Batjer and Duke S. Samson
✓ Giant paraclinoidal carotid artery aneurysms frequently require temporary interruption of local circulation to facilitate safe occlusion. Due to brisk retrograde flow through the ophthalmic artery and cavernous branches, simple trapping of the aneurysm by cervical internal carotid artery clamping and intracranial distal clipping may not adequately soften the lesion. The authors describe a retrograde suction method of aspiration of this collateral supply which they have used in over 40 cases. After temporary trapping, a No. 18 angiocatheter is inserted into the cervical internal carotid artery. This catheter is then connected to a wall suction point allowing rapid aneurysm deflation. This technique, accomplished by the surgical assistant, permits the surgeon the freedom to use both hands in dealing quickly with the aneurysm.
Hunt Batjer and Duke Samson
✓ Only about 5% of intracranial arteriovenous malformations (AVM's) are located predominantly within the ventricular system. Between July, 1981, and February, 1986, 15 patients were treated at the authors' institution for AVM's within the ventricular trigone. The mean age of this patient population was 24 years, and two-thirds were female. Intracranial hemorrhage was by far the most frequent presenting symptom and intraventricular hemorrhage occurred in 11 cases, with multiple episodes being documented in five. Arterial supply of the malformations was quite uniform, with the lateral posterior choroidal or posterior temporal branch of the posterior cerebral artery (PCA) being the most frequent source. Venous drainage was similarly stereotypic, with predominant outflow into the galenic system in all but one patient. An interhemispheric surgical approach was used in eight patients, a middle or inferior temporal gyrus incision was performed in six, and a subtemporal route was chosen in a single patient. Operative results suggest that these lesions can be removed with reasonable safety. An interhemispheric approach is recommended if the nidus projects medially from the trigone and is observed medial to the P2-P3 junction of the PCA on angiography. A middle temporal gyrus approach is suggested if the nidus is lateral to the P2-P3 junction, even when the lesion is located in the dominant hemisphere. A subtemporal approach should be reserved for inferiorly projecting AVM's with cortical representation on the fusiform or parahippocampal gyrus in the nondominant hemisphere.
Phillip D. Purdy, H. Hunt Batjer and Duke Samson
✓ Endovascular embolization procedures have undergone dramatic evolution and improvement in recent years. Despite these advances, controversy remains regarding the optimal role of these procedures in treating cerebral arteriovenous malformations (AVM's) and whether their purpose should be as a presurgical adjunct or as primary therapy. This controversy risks fragmentation between disciplines in the broader efforts to improve management of cerebrovascular disorders.
The authors report seven cases of life-threatening hemorrhages that occurred during staged invasive therapy for AVM's which illustrate the value of a unified team approach to optimize patient care. Each patient underwent at least one embolization procedure using polyvinyl alcohol particles, followed in two cases by the occlusion of proximal feeding vessels by platinum microcoils and in one case by the attempted detachment of an endovascular balloon. In three patients, catheter penetration into the subarachnoid space resulted in subarachnoid hemorrhage. One patient suffered rupture of a large feeding vessel during balloon inflation. The final three patients sustained intracranial hemorrhage 2 hours, 8 hours, and 5 days, respectively, following embolization. All but two patients underwent emergency craniotomy at the time of the complication. These cases underscore the advantages of interdisciplinary management optimizing decision-making and providing expeditious care when life-threatening complications develop.
Cole A. Giller, Kurt Hodges and H. Hunt Batjer
✓ Although blood velocity in the major intracranial vessels is readily measured with transcranial Doppler ultrasound (TCD), the interpretation of velocity changes is by no means straightforward. For example, a velocity increase can arise from either a local stenosis or a decrease in downstream resistance, and these mechanisms have contradictory implications for blood flow. To determine whether TCD pulsatility might distinguish these two mechanisms, Doppler ultrasonic readings were taken from an artificial vascular model under conditions of either stenosis or distal dilation. In addition, TCD studies of nine patients with unihemispheric arteriovenous malformations (AVM's) and 16 TCD studies of seven patients with unihemispheric aneurysmal vasospasm were reviewed, and pulsatilities of the AVM's (representing decreased resistance) were compared with those of the vasospastic vessels (representing stenosis).
The average percentage drop in pulsatility in the vasodilated configuration of the model/percentage increase in velocity was 0.38 ± 0.08 (± standard error of the mean), while that for stenosis was 0.20 ± 0.01. Similar comparisons of the patient population yielded 0.67 ± 0.16 for the AVM group and 0.26 ± 0.04 for the vasospasm group. These differences were significant (p < 0.05). The fall in pulsatility associated with a given increase in velocity is significantly greater when the velocity increase arises from diminished downstream resistance than from stenosis.
Bruno C. Flores, Jonathan A. White, H. Hunt Batjer and Duke S. Samson
Paraclinoid internal carotid artery (ICA) aneurysms frequently require temporary occlusion to facilitate safe clipping. Brisk retrograde flow through the ophthalmic artery and cavernous ICA branches make simple trapping inadequate to soften the aneurysm. The retrograde suction decompression (RSD), or Dallas RSD, technique was described in 1990 in an attempt to overcome some of those treatment limitations. A frequent criticism of the RSD technique is an allegedly high risk of cervical ICA dissection. An endovascular modification was introduced in 1991 (endovascular RSD) but no studies have compared the 2 RSD variations.
The authors performed a systematic review of MEDLINE/PubMed and Web of Science and identified all studies from 1990–2016 in which either Dallas RSD or endovascular RSD was used for treatment of paraclinoid aneurysms. A pooled analysis of the data was completed to identify important demographic and treatment-specific variables. The primary outcome measure was defined as successful aneurysm obliteration. Secondary outcome variables were divided into overall and RSD-specific morbidity and mortality rates.
Twenty-six RSD studies met the inclusion criteria (525 patients, 78.9% female). The mean patient age was 53.5 years. Most aneurysms were unruptured (56.6%) and giant (49%). The most common presentations were subarachnoid hemorrhage (43.6%) and vision changes (25.3%). The aneurysm obliteration rate was 95%. The mean temporary occlusion time was 12.7 minutes. Transient or permanent morbidity was seen in 19.9% of the patients. The RSD-specific complication rate was low (1.3%). The overall mortality rate was 4.2%, with 2 deaths (0.4%) attributable to the RSD technique itself. Good or fair outcome were reported in 90.7% of the patients.
Aneurysm obliteration rates were similar in the 2 subgroups (Dallas RSD 94.3%, endovascular RSD 96.3%, p = 0.33). Despite a higher frequency of complex (giant or ruptured) aneurysms, Dallas RSD was associated with lower RSD-related morbidity (0.6% vs 2.9%, p = 0.03), compared with the endovascular RSD subgroup. There was a trend toward higher mortality in the endovascular RSD subgroup (6.4% vs 3.1%, p = 0.08). The proportion of patients with poor neurological outcome at last follow-up was significantly higher in the endovascular RSD group (15.4% vs 7.2%, p < 0.01).
The treatment of paraclinoid ICA aneurysms using the RSD technique is associated with high aneurysm obliteration rates, good long-term neurological outcome, and low RSD-related morbidity and mortality. Review of the RSD literature showed no evidence of a higher complication rate associated with the Dallas technique compared with similar endovascular methods. On a subgroup analysis of Dallas RSD and endovascular RSD, both groups achieved similar obliteration rates, but a lower RSD-related morbidity was seen in the Dallas technique subgroup. Twenty-five years after its initial publication, RSD remains a useful neurosurgical technique for the management of large and giant paraclinoid aneurysms.
Case report and review of the literature
Stefan A. Mindea, Benson P. Yang and H. Hunt Batjer
✓The authors report on a patient harboring an unruptured cortical arteriovenous malformation (AVM), who had presented with obstructive hydrocephalus due to compression of the cerebral aqueduct by a large venous varix. Although patients with ruptured AVMs are known to either present with or later suffer from obstructive hydrocephalus, those with unruptured AVMs who present in this manner are quite rare. Moreover, hydrocephalus caused by a venous varix draining an AVM, to our knowledge, has never been previously reported in the literature. This report serves to illustrate two primary points, namely, that tortuous venous varices draining AVMs can result in obstructive hydrocephalus and that this unusual circumstance can be fostered in the setting of venous outflow obstruction.
Jing Guo, Jonathan A. White and H. Hunt Batjer
✓ To evaluate etomidate as a neuroprotective agent in the brain stem, 33 dogs were divided into seven groups and were exposed to isolated, reversible brainstem ischemia in the presence or absence of etomidate using a newly developed canine model of brainstem ischemia. Brainstem auditory evoked potentials (BAEP) and regional cerebral blood flow were measured during ischemia and for 5 hours after reperfusion. This model provides a potential physiological environment in which to test the efficacy of putative brainstem ischemic protective strategies.
During ischemia, BAEP were abolished in all animals. Without etomidate 10 minutes of ischemia was of short enough duration to allow complete recovery of BAEP. Ischemia of 20 or 30 minutes' duration resulted in minimal recovery. The dose of etomidate administered did not suppress BAEP or brainstem cardiovascular response to ischemia. In animals receiving etomidate and rendered ischemic for 20 minutes, a significant but only temporary recovery in BAEP was seen. Etomidate failed to have a significant effect in animals rendered ischemic for 30 minutes.
The minimal effect of etomidate on the current measures of brainstem function is in contrast to etomidate's known suppressive effect on cortical electroencephalogram and predicts that etomidate does little to alter brainstem metabolism. Etomidate's failure to provide for permanent recovery of BAEP suggests that the drug does not give sufficient protection from ischemia to the brainstem neurons in the auditory pathway. If these auditory neurons reflect brainstem function as a whole, etomidate may not be the protective agent of choice during temporary arterial occlusion of posterior circulation.