Special case: moyamoya disease and moyamoya syndrome
This is a rare, progressive steno-occlusive disease in which, due to unexplained causes, slowly progressive occlusion of the cerebral arteries in the region of the circle of Willis occurs. In parallel with this, spontaneous intracerebral and also extracranial–intracranial formation of collateral vessels is seen. These are regarded as outstanding examples of the way in which complex natural collaterals can develop on the basis of chronic ischemia. Both steno-occlusive changes with hemodynamically significant impairment of the cerebral blood supply along with spontaneous compensation mechanisms in the form of neoangiogenesis and arteriogenesis are therefore seen in patients with moyamoya disease. In addition to the impressive angiographic findings, the disease is distinct from other steno-occlusive diseases in relation to its epidemiology and clinical course (Fig. 1.2-18). The diagnostic characteristics of moyamoya disease (bilateral lesions, spontaneous collateral network) are more frequently associated with other diseases, sometimes systemic ones. In these cases, the condition is known as moyamoya syndrome. However, this does not generally lead to any changes in the treatment strategy. In central Europe, moyamoya disease and moyamoya syndrome occur sporadically and affect both children and adults. In contrast to the Asian form, which usually becomes manifest in adults in the form of intraparenchymal hemorrhage, cerebral ischemia is the major symptom in both age groups in Europe. Although it is mainly adult patients who suffer TIAs or stroke, the disease can also occur in children, often in the context of focal epilepsy or a cerebral organic psychological syndrome, resulting in inadequate formation of spontaneous collaterals and cerebral compensation mechanisms.
Fig. 1.2–17a, b Intraoperative view. (a) Positioning of the patient for planned placement of a superficial temporal artery (STA)–middle cerebral artery (MCA) anastomosis. The planning incision line (blue) is shown, along with the course of the superficial temporal artery (red) and the planned craniotomy. (b) Completed bypass in the area of the lateral sulcus (sylvian fissure).
Fig. 1.2–18a-c Typical angiographic findings in adult moyamoya disease. There are bilateral steno-occlusive changes in the area of the intracranial carotid bifurcation, with simultaneous formation of extensive basal collaterals.
Indications for revascularization
In view of the poor results of conservative therapy and the underlying pathogenesis of the disease, revascularization surgery is an option for both children and adults. Surgical treatment is indicated in symptomatic adult patients when the diagnosis is confirmed, a reduced CVRC is demonstrated in the symptomatic hemisphere, and there is no severe focal neurological deficit. In children, surgical treatment in both hemispheres is recommended, due to the generally unfavorable natural course of the condition. This allows a marked improvement in the overall prognosis.
Surgical technique
The aim of surgical treatment is to improve the cerebral collateral supply. Various techniques are available for the purpose. In addition to the standard EC/IC bypass described above (STA–MCA anastomosis or STA–anterior cerebral artery anastomosis), which is preferred in adults, there are also a number of indirect procedures. These take advantage of the capacity for spontaneous collateralization. For example, extracranial “donor tissue” can be placed in contact with the arachnoid on the surface of the brain in order to induce spontaneous vascularization with new collateral vessels. This leads to effective revascularization approximately 3 months after the operation. Overall, more than 30 surgical modifications have been described, with indirect revascularization techniques being particularly effective in pediatric patients. Examples of potential “donor tissue” include the temporalis muscle, the epicranial aponeurosis, and the parietal side of the dura mater. In practice, a combination of direct and indirect techniques is used when possible, since in addition to immediate stabilization of perfusion conditions this can also allow delayed synergistic stabilization of regional perfusion. To improve bypass function and for secondary prophylaxis, lifelong medication with platelet aggregation inhibitors is also administered in moyamoya patients.
When combined revascularization is planned, the principles used in direct bypass surgery apply, and these can then be extended, depending on the planned procedure. Combining an STA–MCA anastomosis with encephalomyosynangiosis (EMS) requires an extended craniotomy (Fig. 1.2-19). In this procedure, the temporalis muscle is placed on the cerebral surface after a standard STA–MCA bypass has been created. Regular DSA and MRI examinations are then carried out during the postoperative follow-up. These are useful not only for checking the quality of the surgical procedure but also to assess the subsequent clinical course.
Fig. 1.2–19a, b (a) Positioning of the patient for planned combined revascularization. The planned incision line (blue), the course of the superficial temporal artery (red) and the planned craniotomy have been marked. (b) The intraoperative view after dissection of the temporal muscle, completion of the craniotomy, and resection of the dura mater before placement of the direct bypass.
References
Adams et al. Preview of a new trial of extracranial-to-intracranial arterial anastomosis: the carotid occlusion surgery study. Neurosurg Clin N Am 2001; 12 (3): 613–24, ix–x.
Baker WL, Colby JA, Tongbram V, Talati R, Silverman IE, White CM, Kluger J, Coleman CI. Neurothrombectomy devices for the treatment of acute ischemic stroke: state of the evidence. Ann Intern Med 2011; 154: 243–52.
Baumgartner RW, Mattle HP, Schroth G. Assessment of ≥ 50% and < 50% intracranial stenoses by transcranial color-coded duplex sonography. Stroke 1999; 30 (1): 87–92.
Bose A, Hartmann M, Henkes H, Liu HM, Teng MM, Szikora I, Berlis A, Reul J, Yu SC, Forsting M, Lui M, Lim W, Sit SP. A novel, self-expanding, nitinol stent in medically refractory intracranial atherosclerotic stenoses: the Wingspan study. Stroke 2007; 38: 1531–7.
Bose A, Henkes H, Alfke K, Reith W, Mayer TE, Berlis A, Branca V, Sit SP. For the Penumbra phase 1 stroke trial investigators. The penumbra system: a mechanical device for the treatment of acute stroke due to thromboembolism. AJNR 2008; 29: 1409–13.
Brekenfeld C, Schroth G, Mordasini P, Fischer U, Mono ML, Weck A, Arnold M, El-Koussy M, Gralla J. Impact of retrievable stents on acute ischemic stroke treatment. AJNR 2011; 32: 1269–73.
Chimowitz MI, Lynn MJ, Derdeyn CP, Turan TN, Fiorella D, Lane BF, Janis LS, Lutsep HL, Barnwell SL, Waters MF, Hoh BL, Hourihane JM, Levy EI, Alexandrov AV, Harrigan MR, Chiu D, Klucznik RP, Clark JM, McDougall CG, Johnson MD, Pride GL Jr, Torbey MT, Zaidat OO, Rumboldt Z, Cloft HJ; SAMMPRIS Trial Investigators. Stenting versus aggressive medical therapy for intracranial arterial stenosis. N Engl J Med 2011 Sep 15; 365 (11): 993–1003. Epub 2011 Sep 7.
Derdeyn et al. Cerebral hemodynamic impairment: methods of measurement and association with stroke risk. Neurology 1999; 53 (2): 251–9.
Derdeyn et al. Re: Stages and thresholds of hemodynamic failure. Stroke 2003; 34 (3): 589.
Fiorella DJ, Turk AS, Levy EI, Pride GL Jr, Woo HH, Albuquerque FC, Welch BG, Niemann DB, Aagaard-Kienitz B, Rasmussen PA, Hopkins LN, Masaryk TJ, McDougall CG U.S. Wingspan Registry: 12-month follow-up results. Stroke 2011 Jul; 42 (7): 1976–81.
Gröschel K, Schnaudigel S, Pilgram SM, Wasser K, Kastrup A. A systematic review on outcome