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REVIEW ARTICLE |
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| Year : 2022 | Volume
: 17
| Issue : 5 | Page : 67-76 |
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Management of Chiari 1 malformation and hydrocephalus in syndromic craniosynostosis: A review
Siddharth Vankipuram, Jonathan Ellenbogen, Ajay Kumar Sinha
Department of Neurosurgery, Alder Hey Children’s NHS Foundation Trust, Liverpool, United Kingdom
| Date of Submission | 07-Apr-2022 |
| Date of Decision | 16-Apr-2022 |
| Date of Acceptance | 07-Apr-2022 |
| Date of Web Publication | 19-Sep-2022 |
Correspondence Address:
Dr. Ajay Kumar Sinha
Department of Neurosurgery, Alder Hey Childrens’ NHS Foundation Trust, Liverpool L14 5AB
United Kingdom
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jpn.JPN_49_22
 Abstract | | |
Chiari 1 malformation and hydrocephalus are frequent findings in multi-suture and syndromic craniosynostosis patients. In this article, we review the pathogenesis, clinical significance, and management options for these conditions with comments from our own experience. The role of premature fusion of skull base sutures leading to a crowded posterior fossa and venous outflow obstruction resulting in impaired cerebrospinal fluid (CSF) absorption is highlighted. Management options are unique in this group and we advocate early (prior to 6 months of age) posterior vault expansion by distraction osteogenesis (DO) in the management of Chiari 1 malformation. Foramen magnum decompression is recommended for a select few either as part of posterior vault expansion or at a later date. Treatment of hydrocephalus, utilizing a ventriculoperitoneal (VP) shunt with preferably a programmable high-pressure valve and anti-siphon device, is required in a small percentage of cases despite successful posterior vault expansion. Patients need to be carefully selected and managed as hydrocephalus often serves as an important cranial vault growth stimulus. Further, they require careful monitoring and thought to ensure the management of these conditions and the timing of any intervention provides the optimal long-term outcome for the patient.
Keywords: Chiari 1 malformation, distraction osteogenesis, fibroblast growth factor receptor mutations, posterior fossa decompression, posterior vault expansion, syndromic craniosynostosis
How to cite this article:
Vankipuram S, Ellenbogen J, Sinha AK. Management of Chiari 1 malformation and hydrocephalus in syndromic craniosynostosis: A review. J Pediatr Neurosci 2022;17, Suppl S1:67-76 |
| Introduction | |  |
The association of Chiari 1 malformation (CM) and cerebrospinal fluid (CSF) circulation disorders in complex and multi-suture craniosynostosis is well established.[1],[2],[3],[4],[5] The incidence of ventricular dilatation ranges from 30% to 70% in patients with Crouzon and Pfeiffer syndrome, and between 40% and 90% in patients with Apert syndrome.[3],[5-8] The clinical significance of ventricular dilatation needs to be determined as this terminology includes both hydrostatic hydrocephalus and non-progressive ventriculomegaly. Nonprogressive ventriculomegaly occurs due to either primary brain atrophy, that is, ex vacuo, cerebral maldevelopment, or could simply represent a compensated hydrocephalic state. Differentiation between the two is needed as clearly only hydrostatic hydrocephalus requires active treatment. Studies have reported that insertion of a ventriculoperitoneal (VP) shunt is predominantly necessary for Crouzon and Pfeiffer syndrome patients, and most cases of Apert syndrome represent nonprogressive ventriculomegaly.[6],[7],[8]
Fearon et al. reported a high incidence of CMs in Pfeiffer syndrome patients (84%) and advocated screening magnetic resonance imaging (MRI) for all these patients.[9],[10] Cinalli et al. also published an analysis of CMs detected by MRI in 44 Crouzon syndrome and 51 Apert syndrome patients. They found the prevalence of CM to be 72.7% in Crouzon syndrome and 1.9% for Apert syndrome patients.[3] In another review article, the authors found the prevalence to be 70% in Crouzon syndrome, 75% in oxycephaly, 50% in Pfeiffer syndrome, 100% in the cloverleaf skull, and rare in Apert syndrome patients.[4]
The pathophysiology of both these conditions is related to the small posterior fossa and crowding of its contents, or cerebro-cephalic disproportion, leading to mechanical obstruction of CSF outflow. Premature fusion of skull base sutures, that is, spheno-occipital, petro-occipital, and occipital synchondroses are seen.[4] Venous outflow obstruction also plays an important role. Venous hypertension causes malabsorption of CSF leading to hydrocephalus. It also leads to increased brain parenchymal swelling causing the hindbrain to herniate beyond the confines of the posterior fossa.[3],[4],[7],[11] Fibroblast growth factor receptor 2 (FGFR-2) mutations have been clearly identified in most cases though the exact genetic mechanism is beyond the scope of this review.[4],[11],[12]
Understanding the mechanisms at play is important as management options are unique, and unlike in other non-craniofacial situations. Further, intracranial hypertension is a constant concern in complex craniosynostosis patients even in the absence of overt hydrocephalus. Therefore clinical, radiological, and intracranial pressure (ICP) monitoring is necessary in the management of complex and multi-suture craniosynostosis. In this review, we look at the pathophysiology and management algorithm of such patients. We will deal with each condition separately.
| Pathophysiology | | |
Hydrocephalus
The incidence of hydrocephalus is low and comparable to that of the general population in single-suture craniosynostosis, except possibly that of lambdoid synostosis.[5],[6],[7] Cinalli et al. detected an incidence of 0.88% in a large study of 1447 non-syndromic craniosynostosis patients.[6] Any progressive ventriculomegaly detected in this group is considered to be due to coincidental causes such as intraventricular hemorrhage or stenosis of the aqueduct of Sylvius.[6],[7]
As alluded to earlier, a combination of crowding of the posterior fossa and venous outflow obstruction is the most accepted theory for the development of hydrocephalus.[3],[4],[5],[6],[7] Hydrocephalus can develop rapidly or be slowly progressive, when there is compensation and the ICP may be near normal for some time.[7]
The small posterior fossa (i.e., constrictive theory) causing mechanical obstruction to CSF outflow is classically described as an acquired cephalo-cranial disproportion.[5],[7],[11],[13] It occurs secondary to deficient occipital cranial expansion, which in turn is related to the time of lambdoid suture fusion. The premature closure of the lambdoid suture reflects the premature fusion of the posterior fossa skull base synchrondroses, that is, the spheno-occipital, petro-occipital, and occipital synchrondroses. This is substantiated by the fact that the lambdoid suture closes earlier in Crouzon and Pfeiffer syndromes than in Apert syndrome.[3-5],[7] Consequently, hydrocephalus and CMs are more common in Crouzon and Pfeiffer syndromes. MRI specifically Constructive Interference in Steady State (CISS) sequences reveal obstruction of CSF pathways at the level of extra-cerebral cisterns, whereas the aqueduct is usually patent.[2-4],[6]
Evidence against this theory was described in a paper by Coll et al. where they measured the posterior fossa volume on millimetric CT scans by contouring the space between the cerebellar tentorium, occipital bone, clivus, and temporal bone.[14] They found no differences in volume between healthy patients and those with FGFR-2 induced craniosynostosis patients.
Saint Rose et al. proposed defective CSF resorption due to impaired venous drainage from jugular foramen stenosis as a cause for hydrocephalus (i.e., venous theory).[11],[15] Jugular foramen stenosis increases the sagittal sinus pressure resulting in a higher CSF pressure gradient required to move CSF from the ventricular space into the venous circulation. The effect of the higher CSF pressure gradient depends on the degree of cranial compliance. In infants, the increasing CSF pressure and eventually reduced absorption back into the venous circulation leads to increased size of ventricles and subarachnoid spaces and therefore head size.[4],[6],[11] These patients present early hypothesizing that vascular collaterals open up later with time allowing the venous pressure to normalize. This usually happens by the age of six. In older children with fused sutures, increased venous pressure can produce a pseudotumor-like situation with smaller sized ventricles that can enlarge after decompressive surgery has been performed. The mechanism explains the development of hydrocephalus in Apert syndrome and achondroplasia where ventricular dilation is accompanied by widened subarachnoid space.[11] However, true stenosis of the jugular foramen is often not seen and this leads to the proverbial question of which is cause and which is effect, where the argument is that the hydrocephalic state precipitates stenosis of the venous sinuses and not vice-versa.
Combined mechanisms are most widely accepted in that venous hypertension causes CSF malabsorption, and hydrocephalus, as well as brain swelling resulting in tonsillar herniation or accentuating the preexisting craniocerebral disproportion.[4-7],[16],[17]
Multiple authors have also reported that stenosis at the foramen magnum is important in the pathophysiology.[11],[14],[18-20] They argue that foramen magnum stenosis creates a craniospinal pressure gradient, that is, blockage of subarachnoid spaces increases pressure in the cranial compartment according to Bernoulli’s theorem and the Venturi effect.[11],[14] When a fluid flow is constant and its diameter of flow decreases, pressure decreases downstream of the stenosis and the opposite happens upstream.[11],[21] The dissociation of craniospinal pressure also decreases the subarachnoid craniospinal chamber compliance.[11],[21] A combination of decreased compliance with increased cranial pressure gets transmitted to brain capillaries, with increases in ventricular pulse pressure and pulsatile CSF flow in the aqueduct, and finally global ventricular dilation.[11] Rijken et al. also reported that a small foramen magnum is associated with larger frontal-to-occipital-horn ratio.[18]
This mechanism explains the development of hydrocephalus in Crouzon and Pfeiffer syndrome where the foramen magnum area is narrowed and the subarachnoid space reduced.
Chiari 1 malformation
The incidence of CM (like hydrocephalus) is low in isolated single-suture craniosynostosis. Strahle et al. conducted a retrospective analysis of CT and MRI scans in 343 patients with isolated, non-syndromic, non-lambdoid suture involvement craniosynostosis: 183 sagittal, 71 metopic, and 80 coronal suture synostosis.[22] Of these patients, 5 (2.8%), 0 (0%), 5 (6.3%), respectively, showed tonsillar herniation of greater than 5 mm (the radiological definition of a CM). Which is in most cases asymptomatic and only diagnosed on surveillance MRI imaging.[1],[22] Specifically, Strahle et al. reported that the incidence of CM is high in multi-suture, complex, and lambdoid suture synostosis and this knowledge guides the need for screening MRI scans.[22]
The incidence of CM is high in complex craniosynostosis especially in patients with Crouzon and Pfieffer syndromes and low in Apert syndrome.[3],[4],[22] There is no doubt that CM is an acquired pathology and de novo development has been reported.[22] Thompson et al. postulated that hindbrain herniation in complex craniofacial syndromes occurs as a result of two factors:[2]
- High mean ICP, that is, excess pressure above the foramen magnum. This can however not occur alone as there are many conditions of raised supratentorial ICP without any hindbrain herniation.
- Posterior fossa size: In their study in 1997, they demonstrated an inverse relationship between the size of the posterior fossa and degree of hindbrain herniation. They found that a small posterior fossa, or cephalo-cranial disproportion, is associated with CM. The size is influenced by the functional integrity of the skull base synchondroses, and these sutures are often fused earlier.
As mentioned previously, Cinalli et al. reported that the spheno-occipital, petro-occipital and occipital synchondroses fuse early in Crouzon syndrome, whereas they never fuse early in Apert syndrome.[2],[3] Further, any posterior fossa growth in Crouzon syndrome is along the superior-inferior axis and there is very restricted growth along the antero-posterior axis. Fusion of the petro-occipital synchondroses could also lead to jugular foramen stenosis, venous hypertension and accentuate the development of CM due to increased brain turgor.[4],[23] As a visualization of these skull base synchondroses is difficult on X-rays, the patency of the lambdoid sutures is often taken as a marker. The precocious closure of the lambdoid sutures (within the first year of life) has served as a radiological marker for synostosis of posterior skull base synchondroses and accordingly, this is seen more commonly in Crouzon syndrome than Apert syndrome.[3]
However, this cannot be the only phenomenon as CMs occur very frequently in oxycephaly where there is no fusion of skull base synchondroses.
| Co-existence of Chiari 1 Malformation and Hydrocephalus | | |
The co-existence of CM and hydrocephalus is well documented in the literature.[2-4],[6],[7],[11],[14],[24] Data from different studies suggest that CM is necessary though not fully sufficient to explain the development of hydrocephalus and similarly, hydrocephalus alone cannot be the driving force to create acquired CM.[2],[4] Foramen magnum stenosis aggravated by a CM can worsen the hydrocephalus and lead to a vicious circle.[11]
Tonsillar ectopia is present to a variable degree in almost all cases of progressive ventriculomegaly and therefore more commonly seen in Crouzon and Pfeiffer syndrome, whereas is rarely seen in Apert syndrome.[2],[7],[11] Cinalli et al. showed that for Crouzon syndrome, all hydrocephalic patients have CMs and 53% of patients with CM are hydrocephalic.[3],[4],[6] Coll et al. showed in their series that 83% of hydrocephalic children with Crouzon or Pfeiffer syndrome had CM whereas 62.5% of Crouzon or Pfeiffer syndrome children with CM were hydrocephalic.[14] Strahle et al. reported that 15 out of 29 (52%) patients with CM had hydrocephalus.[22]
In these situations, venous sinus stenosis could play a predominant role. The degree of venous stenosis is more prominent in patients with Fibroblast Growth Factor Receptor 3(FGFR-3) mutations and less with FGFR-2 mutations. Venous hypertension increases the CSF pressure gradient and leads to malabsorption of CSF ultimately causing hydrocephalus. It also leads to increased brain parenchymal swelling and decreased compliance. Eventually, the hindbrain herniates beyond the confines of the posterior fossa. If the sutures are open, the increased CSF pressure leads to increased ventricular size and hydrocephalus while if the sutures are closed, it could result in a pseudotumor-like state.[2],[4],[11]
Proof of the role of venous hypertension can be demonstrated in Vein of Galen aneurysms treated by Girard et al. who showed that the hindbrain herniation reverses following endovascular treatment.[24],[25]
| Clinical Evaluation and Diagnosis | | |
Shunt-dependent hydrocephalus is diagnosed based on progressively enlarging ventricles and clinical signs of raised ICP.[6],[7] In 50% of children with complex craniosynostosis, it is not straightforward because:
- The abnormal head shape can lead to disproportionate head growth and therefore, increasing occipitofrontal head circumference is not always noted and therefore cannot be used as a guide. For example in Apert syndrome, premature involvement of bilateral coronal sutures often produces a turricephaly-like appearance.
- Ventricular size and markers, such as a dilated third ventricle or temporal horns, cannot reliably be used to identify hydrocephalus (especially in the postoperative period) as there is always some degree of ventricular dilatation following surgery for craniosynostosis.[5],[7]
- Most of these patients have persistent intracranial hypertension irrespective of ventricle size and therefore identifying symptomatic hydrocephalus becomes challenging.[12]
- Distinction between nonprogressive ventriculomegaly and hydrostatic hydrocephalus is also often difficult.
In a good proportion of cases, ventricular dilatation only really develops after decompressive surgery for the craniosynostosis.[6],[7] Identification of symptomatic hydrocephalus in this group relies on the identification of persistent raised ICP.[5],[7] In many instances, it is prudent to wait rather than treat straight away as: (1) The increase in cranial volume created by surgery will be accommodated to some degree by an increase in intra-cerebral and extra-cerebral CSF spaces giving the appearances of dilatation. (2) Signs of raised ICP like papilloedema take a few weeks to settle.
Clinical signs and symptoms of hydrocephalus may include drowsiness, vomiting, refusal of feeds, increasing head circumference, tense anterior fontanelle with prominent scalp veins, and sunsetting eyes. Associated features such as the type of suture involved, syndromic or nonsyndromic synostosis, and patency of lambdoid suture can help to indicate whether or not there is a higher chance for the development of hydrostatic hydrocephalus.
Around one-third of craniosynostosis patients with tonsillar ectopia become symptomatic. Symptoms range from sub-occipital neck pain to life-threatening brainstem dysfunction.[3],[4] In younger patients, the clinical presentation could be more dramatic for example; central apnea, bilateral vocal cord paralysis, bulbar palsy, ventilatory control abnormalities, persistent cyanosis, and breath-holding spells.[4]
In a study by Fearon, 10 out of 21 (48%) Pfeiffer syndrome patients with CM received surgical decompression of the foramen magnum because of symptoms, that is, swallowing and coordination problems, headache when coughing, development of syrinx and central apnea.[9]
CT head scans are routinely performed in all cases and should include 3D CT reconstruction to evaluate the patency of sutures. CT images also identify the central keel in the foramen magnum that requires removal if a foramen magnum decompression (FMD) is being planned. MRI imaging in complex craniosynostosis syndromes should include CISS (CSF drive) sequences to evaluate CSF flow and the significance of the CM in terms of CSF flow around the foramen magnum. CT/MR venography identifies venous sinus stenosis and the development of venous collaterals.[5],[6],[26] The presence of crowding of the posterior fossa or gross ventricular dilatation on imaging warrants monitoring with ophthalmoscopy, optical coherence tomography (OCT), and if needed ICP monitoring. Caution needs to be exercised though in young children as papilloedema may not be evident even in patients with raised ICP.
When there is equivocal non-invasive evidence of raised ICP, invasive ICP monitoring is required. In our experience, using intraparenchymal pressure sensor devices for a continuous period of 48 h provides valuable information regarding the presence of intracranial hypertension. We usually perform a right frontal twist drill craniostomy and insertion of an intraparenchymal ICP probe. Identification of abnormal B waves, duration of elevated ICP and ICP recording at night to detect spikes is performed. The possibility of compensated hydrocephalus should also be kept in mind and these patients should be under careful surveillance.
| Treatment | | |
Chiari 1 malformation
Treatment options for symptomatic CM include posterior vault expansion with or without posterior fossa decompression. Sgouros et al. recommended early posterior vault expansion for multi-suture synostosis patients in 1996.[10] Techniques described by them include a single circular occipital craniectomy or two free bone flaps with excision of midline bone. In both techniques, the goal is to release synostosed lamboid sutures bilaterally. Others advocate the policy of early remodeling of the posterior cranium, followed by anterior Fronto-Orbital Advancement and Remodeling (FOAR). Early correction of the occipital flattening allows the reduction of ICP and defers the FOAR procedure, reducing the occurrence of recurrent craniosynostosis, which would require late re-operation.[10],[27],[28] FOAR is required to enlarge the frontal fossa, advancing the orbital bandeau anteriorly, and protecting the globe.[9]
Posterior expansion allows for an increase in intracranial volume with minimal cosmetic detriment as the frontal areas are left undisturbed. The intracranial volume gained per millimeter of distraction is greater when the posterior calvarium is expanded compared to an equivalent distance of fronto-orbital advancement. A recent study demonstrated that posterior vault expansion using distraction osteogenesis (DO) provides a two times greater volume gain than single-stage fronto-orbital advancement.[29] Volumetric data for three different posterior cranial vault expansion techniques have been compared demonstrating an expansion of 13–24% for posterior cranial vault expansion by free-floating parieto-occipital bone flap, 18–25% for translambdoid springs, and 22%–29% for internal distractors.[30] Another study found increases of up to 28.5% of the intracranial volume were possible utilizing posterior cranial vault distractors.[31] Although posterior distraction techniques are inherently more difficult to maintain in position and prevent shape relapse, as when sleeping supine, the weight of the child’s head will tend to force the repositioned fragment back into its original position. Certainly, the significantly less complex bony anatomy of the posterior vault and the tolerance for small asymmetries make distraction in this region a much more forgiving endeavor than it is in the fronto-orbital region.
Posterior vault expansion is sometimes treated as a two-stage approach. Performing an early posterior cranial vault expansion to achieve a large increase in intracranial volume, and then secondly to perform a standard FOAR at a later stage if required, to correct the morphology of the anterior skull vault. FOAR may be required for definitive correction of the retrusive brow and orbits seen with syndromic craniosynostosis and improve overall aesthetics. Therefore the first volume-expanding procedure buys time and gives the ability for the FOAR to occur at a time point when a more permanent morphological result can be achieved. Moreover, posterior cranial vault expansion has the potential to relieve any local compression on the brain in the posterior cranial fossa. In patients with progressive hydrocephalus, decompression of the sub-tentorial compartment should theoretically enhance CSF flow for the reasons alluded to above.[30]
A study looking at forty children with syndromic craniosynostosis, found only 61% of patients who underwent initial posterior vault DO required frontal advancement and remodeling, at a mean follow-up of 4 years of age, compared with 100% of patients before implementation of posterior vault DO techniques. They found utilizing early posterior vault DO for patients with syndromic craniosynostosis significantly reduced the average number of fronto-orbital advancement procedures in the first 5 years of life, delayed the initial fronto-orbital advancement, and was likely to reduce the total number of major craniofacial procedures.[32] A possible reason for this is that, unlike anterior vault distraction, posterior expansion of the cranium appears to decrease frontal bossing and to decrease cranial height trajectory.[33]
In infants with severe CM, a one-step operation to correct occipital flattening and CM has been proposed.[34] The scalp flap is reflected posteriorly to the inion where occipital musculature is elevated subperiosteally. This allows exposure up to the posterior ridge of the foramen magnum. The parietal and occipital bones are then removed and the torcula and transverse sinuses are dissected off the bone. This allows access into the posterior fossa to the lip of the foramen magnum, which must be carefully dissected from the periosteum. Bony decompression is then done either piecemeal or in en bloc fashion. The occipital foramen is opened wide laterally to avoid long-term failure secondary to the re-growth of bone.[3],[4],[35] Strahle et al. performed simultaneous posterior vault expansion and CM decompression in 5 of the 17 patients diagnosed with CM before craniosynostosis repair.[22] These infants who undergo craniosynostosis repair very early on in life require a second operation 6 to 12 months later once the bone is thicker permitting a more stable construct.[9]
In older patients (>1 year), total calvarial reconstruction to correct the significant deformity secondary to bicoronal and bi-lambdoid synostosis can be performed. When both fronto-orbital advancement and occipital remodeling are planned, one-step or multiple-step procedures can be employed. The one-step procedure is performed with the child in the “modified prone position,” described by Pollack et al.[36]
In our unit, older children undergo posterior vault expansion by DO.[35] DO is a process whereby traction is applied between two surfaces of cut bone gradually increasing the distance between the fragments and thereby promoting bone growth to fill in the divide left behind [Figure 1]. By progressively expanding the distance between the fusing ends of the calvarial bones the intracranial volume may be gradually increased, allowing subsequent fusion to occur in a more normalized position. Cranial vault distractors allow direct precise control of the distraction of the vault components, allowing control of the rate of distraction, the amount of distraction, and when to stop distraction. They also enable the components to be held stable for the consolidation period to prevent relapse of the fragments back to their original positions. Cranial vault distractors have been shown to be an effective and safe method for vault expansion. An average distraction distance of 24 mm can be obtained.[37] Ahmed et al. reported improvement in symptoms of raised ICP, Chiari malformation and syringomyelia after posterior distraction in a case of complex multisutural craniosynostosis secondary to Crouzon’s syndrome, although the radiographic improvement lagged behind by about 12 months.[38] A number of studies have confirmed that distraction reduces operative blood loss, decreases operative time, and lowers number of days spent in the intensive care unit and in the hospital.[39],[40],[41] | Figure 1: Posterior vault expansion via distraction osteogenesis schematic
Click here to view |
FMD can be specifically reserved for those subset of patients with CM who are symptomatic or who have spinal cord synrixes.[22] Preoperative CT scan determines the need for excision of the central bony keel during FMD. Dural decompression is generally never required as there is a risk of severe bleeding due to venous anomalies.[22]
When CM is diagnosed or becomes symptomatic later in life, it should be managed like any other CM requiring surgical treatment, with the same indications for surgical treatment or simple radiological follow-up as in any non-craniosynostosis patient. The only major difference is in the preoperative radiological evaluation: patients with CM and craniosynostosis, especially if syndromic or associated with hydrocephalus, are likely to present with abnormal venous drainage, which must be correctly studied with preoperative vascular imaging to minimize the risk of catastrophic blood loss.[3],[4]
The Rotterdam working group has recommended:[1]
- 1. Screening by MRI for presence of CM in
- I. non-syndromic unilambdoid craniosynostosis
- II. Crouzon/Pfeiffer syndrome
- III. multi-suture synostosis with involvement of lambdoid suture
- 2. MRI is repeated at age of 4 years, 18 years or when there is clinical suspicion of symptomatic CM
- 3. MRI spine is included to look for the presence of syringomyelia.
- 4. Annual check-up for neurological symptoms or signs
Cranial vault distractor operative technique
The patient is placed prone on the operating table utilizing a Horseshoe headrest or similar to support the head. It is imperative that the contact points of the face with the headrest (i.e., cheeks and forehead) are adequately padded and protected from pressure, and that there is no direct pressure on the orbit/eyes. It is also important to ensure that all possible body pressure points are well padded to prevent the development of pressure sores. The patient is then prepped and draped in the standard fashion, allowing room for the arms of the distractor to be brought out through the skin. The scalp incision is carried out through a “wavy line” or “zig-zag” coronal incision anterior to the vertex of the skull [Figure 2]. The galea is dissected from the underlying periosteum, leaving as much of the loose areola tissue on the periosteum as possible, and reflected on an inferior pedicle below the level of the transverse sinus/torcula. The pericranium is not lifted off the skull bones and only incised along the lines of proposed craniotomy [Figure 3]. This minimizes venous bleeding from numerous emissary veins that traverse the skull bones. The posterior cranium is then exposed allowing the craniotomy to planned as required. The authors always prefer to carry out a large craniotomy and take the posterior cuts as low as possible. It is not necessary, and indeed causes unnecessary risk of venous injury, to try and detach the underlying dura from the released posterior cranial vault. The cranial vault distractors are then fixed to the bone on either side of the skull osteotomies to provide a posterior vector of distraction, and we prefer to use one distractor on either side. It is important that the distractors are positioned to provide a uniform parallel vector of distraction to avoid complications from device stress caused by converging vectors [Figure 4]. It is helpful to bend the fixation plate of the distractor to the contour of the outer skull table enabling it to lie as flat as possible. Each device is secured with titanium flat tipped screws, in order to minimize the risk of the dura being torn as the screw is pulled over the surface of the dura during distraction. The authors always insert a piece of gelfoam between the bone and the underlying dura at the site of distractor plates, in order to avoid the screws catching the dura during the process of distraction. Depending on surgeon’s preference, and the shape of the child’s head, the arms of the distractors are brought out through stab incisions anteriorly or posteriorly [Figure 5]. All incisions are then closed without the placement of drains. Distraction may then commence 5–7 days following distraction placement. The rate of 1 mm/day is applied with a frequency of three turns per day (0.3 mm per turn). Parent education takes place in the postoperative period and they continue to perform their child’s distraction at home. Once the desired/maximal distraction is achieved the distraction arms are removed utilizing the quick-disconnect couplings. The cranium can usually be distracted between 20 and 30 mm [Figure 6]. Time is left for the consolidation of new bone growth to occur, typically 6 to 8 weeks. Patients have skull X-rays during the latency phase, midway through distraction, and at the end of distraction to ensure distraction in progressing and to confirm bone infill. A second short general anesthetic is required to remove the distractors through a limited opening of the original coronal incision, approximately 3 months following initial placement.[42] | Figure 2: Prone patient positioning and padding demonstrated together with the “zig-zag” coronal incision
Click here to view |
 | Figure 3: Pericranium not lifted off the skull bones and only incised along the lines of proposed craniotomy
Click here to view |
 | Figure 4: Cranial vault distractor fixation plates are contoured to the outer skull then fixed to the bone on either side of the skull osteotomies to provide a posterior vector of distraction
Click here to view |
 | Figure 5: Arms of the distractors are brought out through stab incisions anteriorly
Click here to view |
 | Figure 6: Head CT reconstruction demonstrating that the cranium can usually be distracted a significant length (usually 20–30 mm)
Click here to view |
Hydrocephalus
The treatment of hydrocephalus in complex craniosynostosis is carefully nuanced in terms of identifying those patients who need intervention as well as determining the timing and choice of appropriate intervention.
In syndromic craniosynostosis, intracranial hypertension is constant even in the absence of active hydrocephalus and therefore radiological monitoring of ventricular size along with ICP is mandatory to prove the presence of hydrostatic hydrocephalus.[14] Our experience is to perform craniosynostosis corrective/expansive surgery in such patients and then monitor the progression of ventricular size before committing to CSF diversion. A point to note is that nonprogressive ventriculomegaly may evolve into overt hydrocephalus after cranial expansion and close monitoring is necessary.[12]
Treatment options include:
- Posterior cranial expansion: Advocated in infants and performed usually prior to 6 months of age. The procedure of DO as mentioned above, with or without posterior fossa decompression based on the presence of an associated CM. This would help as an initial step in dealing with the raised ICP though it does not always reverse the hydrocephalus.[34]
- VP shunt insertion: As mentioned, vault expansion or suturectomy is first considered in the management algorithm for all patients. Need for a VP shunt at a future setting can be determined based on increasing head circumference and ventricular size. When considering VP shunt, it is ideal to prevent over-drainage and secondary synostosis. It is our practice to generally incorporate a high pressure programmable valve with inbuilt or external anti-siphon device. The benefit of using a programmable valve is that the pressure can be slowly reduced over time to a more normal pressure once the main bulk of cranial vault growth/remodeling has occurred and brain drive is no longer required to ensure adequate cranial skull vault size. The timing of shunt surgery is important as the rapidly drained CSF spaces get filled by growing brain while at the same time depriving the skull of an important growth stimulus.[5],[43] Excess drainage of CSF may result in fusion of normal sutures and secondary synostosis.[43] Known anatomical landmarks like Keen’s or Kocher’s point are often distorted due to the disproportionate skull shape. Our experience is to use image guidance (electromagnetic [EM] guidance) for ventricular catheter placement to ensure correct placement. The site of catheter placement is based on planning for possible future surgeries, such as a fronto-orbital advancement or FMD. When future craniofacial procedures are performed in the presence of a shunt, we leave an island of bone around the ventricular catheter and reservoir to protect it from any distraction effects of the craniosynostosis repair.
- Endoscopic third ventriculostomy: Especially useful when there is evidence of obstructive hydrocephalus at the level of foramen magnum.[43] Theoretically, it would avoid intracranial hypotension known to occur with VP shunts and prevent secondary synostosis. Di Rocco et al. studied 11 patients with syndromic craniosynostosis who underwent ETV. These patients were carefully selected after MR imaging revealed obstruction to CSF flow making ETV likely to succeed. All their patients above 6 months of age did well, whereas two of their remaining five patients under 6 months did not need a shunt.[43]
Both ETV and VP shunt do not treat the venous stenosis with the intention that eventually enough collaterals form to bypass the high venous pressure state. In our unit, venous sinus stenting is not performed routinely and there is limited evidence for its scope in the management of these patients.
| Conclusion | | |
CM and hydrocephalus are acquired progressive conditions that develop in the first few months of life in complex multi-suture and syndromic craniosynostosis patients. These patients require careful monitoring and thought to ensure the management of these conditions and the timing of any intervention provides the optimal long-term outcome for the patient. As such the craniofacial team consists of a large number of medical and allied professionals to provide a holistic approach to the management of these complex craniosynostosis patients.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Not applicable.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
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