Childs Nerv Syst DOI 10.1007/s00381-015-2802-7 CASE REPORT Decompressive hemicraniectomy in the management of acute stroke in children with Moyamoya disease: the difficult balance between the spontaneous postoperative revascularization process and the need for cranial reconstruction Marc Hohenhaus 1 & Mukesch Johannes Shah 1 & Matthias Eckenweiler 2 & Vera van Velthoven 1,3 Received: 29 January 2015 / Accepted: 22 June 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Back grou nd a nd imp orta nc e The dec omp ressi ve hemicraniectomy (DCH) after malignant middle cerebral artery infarction in children is a rare procedure, and the indication is discussed as being controversial. Etiological Moyamoya disease has some additional challenges concerning the therapeutic strategy that have not mentioned in the recent literature, as it is dependent on special pathophysiology. Clinical presentation We report a case of a four-year-old patient with a decompressive hemicraniectomy after malignant middle cerebral artery infarction on the right hemisphere based on a Moyamoya syndrome with proximal MCA occlusions on both sides. After the decompression there was a good restitution of the hemiparesis, aphasia, and consciousness loss on admission. The bone flap replacement is usually done after three month in our department to ensure brain swelling has subsided. In this patient the cranioplasty was not arranged because of the development of collateral vessels to the right motor region through the craniotomy defect, to protect the supply of the eloquent cortex. There are no financial affiliations for each of the authors. * Marc Hohenhaus marc.hohenhaus@uniklinik-freiburg.de 1 Department of Neurosurgery, University Medical Center Freiburg, Breisacher Strasse 64, 79106 Freiburg, Germany 2 Department of Pediatrics, University Medical Center Freiburg, Mathildenstrasse 1, 79106 Freiburg, Germany 3 Department of Neurosurgery, University Hospital UZ Brussel, Laarbeeklaan 101, 1090 Brussel, Belgium Conclusion We conclude that the indication of DCH and postoperative treatment should be discussed individually, especially when neovascularisation developments can occur like in Moyamoya disease. An important point is the right timing for bone flap replacement, which should be directly after cerebral edema has subsided prior to the evolution of collaterals through the craniotomy defect. Additionally, leaving the opportunity for neovascularization through smaller defects has to be taken into account. Keywords Bone flap replacement . Cranioplasty . Decompressive hemicraniectomy . Infarction . Moyamoya Background and importance Acute ischemic stroke (AIS) is a rare pathology in children with an overall incidence of 0.5-8/100000 per year [1–5]. Different underlying pathologies can be detected, especially arteriopathies (53 %), cardiac disorders (31 %) and acute or chronic systemic conditions (41 %) like sepsis or sickle cell disease, whereupon 52 % have multiple risk factors [6]. In case of malignant ischemic stroke, conservative therapy in space-occupying cerebral edema is associated with fatal outcome in about 80 % of the patients [7]. Decompressive hemicraniectomy (DCH) improves neurological outcome and decreases mortality in adults significantly, which was shown in different randomized controlled trials (RCT) [8]. In pediatrics this intervention has not been investigated in RCTs as yet. In some small case series of children, however, it was shown that DCH can be life-saving in cases of extensive brain swelling [9–12]. In contrast to the adult population, where DCH has to be performed within 48 hours after onset of symptoms, the time period seems to be more expandable [11, 13]. Childs Nerv Syst The DCH after AIS in patients with Moyamoya disease was not reported in the literature yet and seems to be challenging because of associated pathophysiological factors. Moyamoya disease is a very rare progressive, non-atherosclerotic, occlusive disease of the distal internal carotid artery (ICA), proximal medial cerebral artery (MCA), and anterior cerebral artery (ACA) [14, 15], described in up to 9 % of AIS in the pediatric population [6]. There is a high geographical variability of the incidence with 0.54-0.95/100000 per year in Japan [16, 17], compared to, e.g., 0.086/100000 per year in the USA, while the incidence in Asian Americans seems to be as high as in Asia [18]. Typically both hemispheres are affected, and primarily the posterior circulation is uncommonly involved [19]. Depending on the pathophysiological development and the age of the affected patients, there are two different clinical presentations. Because of occlusions of the brainsupplying arteries without adequate collateralization, transient ischemic attacks and strokes are primarily common in children [20]. As a result of the chronic ischemia, there is a formation of small collateral vessels, so-called BMoyamoya vessels^, with special histological structure [21]. Because of the high vulnerability of these vessels with associated microaneurysms and increased blood flow, the probability of ruptured vessels and resulting intracerebral and subarachnoidal hemorrhage is increased [20, 21]. This is the typical presentation of the adult population in Moyamoya disease. We report a case of a four-year-old patient with a DCH after malignant MCA infarction based on a Moyamoya syndrome. The indication of DCH and following problems in the postoperative care are discussed. Fig. 1, 2 Diffusion-weighted MRI sequence with acute MCA right infarction Clinical presentation The male patient presented with the first symptomatic ischemic stroke at the MCA and posterior cerebral artery (PCA) territory at the age of 13 months with a transient hemisyndrome on the left side. A MRA in the diagnostic work-up showed typical signs for Moyamoya syndrome like high-grade stenosis of the distal internal carotid artery on both sides with surrounding small BMoyamoya vessels^ at the region of the Circulus Willisii. In his medical history there were additionally an unclassified chronic dermatosis, a severe atypical haemolytic uremic syndrome at the age of four months, a subsequent arterial hypertension, and a chronic hemolysis. The actual findings were classified as Moyamoya syndrome, but there was no interdisciplinary presentation of the patient for the evaluation of further treatment options at that time. Our first contact with the patient was about three years later when he was admitted with an acute left hemiparesis, aphasia, and progressive reduced level of consciousness. MRI showed a subtotal MCA infarction at the right hemisphere with a compressive midline shift (Figs. 1 and 2). MRA showed an associated proximal MCA occlusion on both sides (Figs. 3 and 4). The neurosurgeon on call decided for an emergency DCH because of the space-occupying cerebral edema. The operation was done without any surgical complications within 12 hours after symptom onset. Postoperative imaging showed a progressive infarction with involvement of the whole MCAand parts of the ACA-territory on the right side, but with a good decompressive effect of the surgical treatment (Figs. 5 and 6). Postoperatively, the patient regained consciousness, the hemiparesis improved, and he showed a good speech comprehension. In the subsequent rehabilitation he regained active speech. A follow-up MRI after three months showed a recurrent brain swelling at the old defect area and a persistent ICA occlusion on the right side. A complementary digital subtraction angiography (DSA) showed a partial supply of the right central region through collaterals originating from the external carotid artery (ECA) through the craniotomy defect (Figs. 7 and 8). Additionally, there were typical BMoyamoya vessels^ Childs Nerv Syst Fig. 3, 4 Time-of-flight MRA with typical presentation of distal ICA and proximal MCA occlusion on both sides surrounding the MCA occlusion on the right side (Fig. 7). Because of the collateral supply through the skin flap, no Fig. 7, 8 Digital-subtraction angiography of the right ECA showing collaterals to the right central region through the craniotomy defect (Δ) replacement of the skullbone could be performed. The neurological restitution went on, so that the patient currently is able to walk without any orthesis with a moderate residual left hemiparesis, and he shows significant advances in speech and cognitive development on the level of a mild cognitive retardation. Besides, an indirect vascularisation of the left hemisphere was stimulated by multiple burr holes with insertion of periost flaps nine months after the malignant stroke. Till now, the right-sided defect is still covered by a protective helmet without any further surgical treatment. Discussion Fig. 5, 6 Postoperative FLAIR MRI sequence with good decompressive effect and demarcation of the whole infarct territory We present a rare etiology for malignant MCA infarction with therapeutic DCH and a complicated postoperative course because of the pathophysiology of Moyamoya disease. In the adult population DCH is clearly associated with improved neurological outcome in malignant MCA infarctions Childs Nerv Syst when it is done within 48 hours after onset of symptoms [8]. In pediatric patients there are only a few reports, but none concerning Moyamoya disease. Overall, it can be recommended that in a life-threatening cerebral edema the DCH is an effective solution for saving life and the best neurological outcome for the patient [11]. because of the early revascularization through the dura defect, the patient recovered rapidly from his clinical symptoms with a satisfying restitution of neurological functions. The solution certainly would have been to replace the bone flap as early as the brain swelling permitted, but leaving an opening for myosynangiosis in order to make collateral circulation possible. What to do after the hemicraniectomy? What was the treatment in our case? In the case of Moyamoya disease, fulminant neovascularisation arises in the area of vessel occlusion through collaterals from the external circulation [20]. For inducing growth factors, like VEGF, bFGF or HIF-1, a higher expression in Moyamoya patients can be detected [22]. This proangionetic cerebral milieu is taken advantage of for therapeutic indirect revascularization interventions, like Encephalo-Duro-ArterioSynangiosis (EDAS) or Encephalo-Myo-Synangiosis (EMS) [20]. Therefore, the collateralization through the hemicraniectomy defect and associated difficulties for cranioplasty could have been expected in our case. Definitive treatment of the right-sided craniotomy defect was discussed intensively. The construction of direct revascularisation for the supply of the right hemisphere was not possible because the origin of the naturally developed collaterals from each potential donor vessel from the external carotid artery. The supply was generated from the superficial temporal artery branches and occipital arteries too. Another opportunity to close the defect with the help of partial bone fragments surrounding the naturally developed bypasses was rejected by the parents of the patient, because of potential new neurological deficits, which could be induced by disturbing the actually effective supply. What’s the right timing to replace the bone flap? There is no consensus for early or late cranioplasty after DCH in recent literature [23–27]. In our department the dura mater is left open after DCH and the bone replacement is standardized three months after DCH to ensure brain swelling has subsided. In the presented case the time period seems to be too long because of the development of external collateralization through the craniotomy defect. Removal of the skin flap to reconstruct the bone defect could tear out the collateral vessels with a high risk of a following ischemia in the vital eloquent cortex. So the cranioplasty was not arranged to preserve the cerebral supply. Conclusion We conclude that the indication of DCH and postoperative treatment should be discussed individually, especially when neovascularisation developments can occur like in Moyamoya disease. An important point is the right timing for bone flap replacement, which should be directly after cerebral edema subsides prior to the evolution of collaterals through the craniotomy defect. Additionally, leaving the opportunity for neovascularization through smaller defects has to be taken into account. How to catch the right point? The bone flap replacement certainly should have been done as early as possible after reduced cerebral edema. A higher rate of bone flap resorption after cranioplasty is postulated when it is done within 2 months after the decompression in adults, so that a very early replacement could be associated with increased complications too [28]. There is only small evidence yet in the literature and no isolated information for pediatric patients. The point of the beginning of vessel engraftment is described at about three to four months in indirect revascularization procedures [20]. In our case, however, the neovascularization was fully established at this time. So we conclude that the development of the neovascularization should be investigated individually in every patient. In order to prevent the collateralization through the craniotomy defect, a closure of the dura mater by aid of synthetic materials like a polyethylene mesh could be envisaged. On the other hand, probably References 1. 2. 3. 4. Fullerton HJ, Wu YW, Sidney S, Johnston SC (2007) Risk of recurrent childhood arterial ischemic stroke in a population-based cohort: the importance of cerebrovascular imaging. 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