Decompressive Cranioplasty using Titanium Mesh in a Patient with Osteopetrosis: A case-based Reviews.

Abstract

Introduction: Osteopetrosis is an inherited disease that causes thickening of the cranial bone. The need for both cerebral decompression and intracranial volume-enlarging cranioplasty in the same surgical session in a patient whose intracranial pressure is elevated cannot be prevented and is a very rare decision in neurosurgery practice. It is seen in the literature that the only indication that can lead to this surgery is osteopetrosis.

Case report: A 24-year-old female patient with osteopetrosis admitted with the complaint of severe headache that did not respond to medical treatment, and surgery was decided. After decompressive craniectomy was performed with difficulties, cranioplasty with titanium mesh was performed in the same session to protect the cerebral tissue, to close the defect area, and to give more space to the cerebral tissue.

Conclusions: It was observed that the complaints of increased intracranial pressure were completely resolved with unilateral cranial decompression in the early postoperative period and at the end of 2 years. The surgical intervention technique performed on the patient and the radiological findings obtained during the follow-up are presented. We think that performing cranioplasty with titanium mesh, which is used to protect and save the cerebral tissue in patients with osteopetrosis, is the most appropriate choice.

Introduction

Intracranial hypertension is a critical event frequently occurring after traumatic brain injury (TBI) as a delayed secondary pathologic process initiated at the moment of injury. Due to the rigid nature of the skull and the dura, brain edema, expanding hematomas, or blossoming of contusions can rapidly exhaust the compensation mechanisms leading to maintenance of a controlled intracranial pressure (ICP). Following failure of medical management, decompressive craniectomy (DC), a procedure consisting on removal of part of the skull and opening of the underlying dura, can be used as a last-tier therapy to mitigate ICP elevation. DC used as a last-tier therapy for patients with severe, sustained, and refractory posttraumatic intracranial hypertension leads to a substantial mortality reduction. In patients with osteopetrosis with increased intracranial pressure, the need for decompressive craniectomy becomes essential as reported in the literature [1, 2].

However, since the increased intracranial pressure decreases when the cranial volume expands, it is necessary to close the cranium again in the same session. Both bone flap removal and cranioplasty are accomplished at the same time. The procedure of Decompressive Bone Flap Replacement (DBFR) is capable of preserving the skull integrity and achieving a decompressive effect. The increase in intracranial pressure in osteopetrosis is not very high. In the same surgical session, the cranial defect can be closed again either with its own thinned cranial flap or with a titanium mesh graft. There are different opinions about which one is more suitable for cranioplasty in osteopetrosis. However, we have obtained findings supporting the literature that cranioplasty with titanium mesh is a more accurate choice [3]. After acute phase, the intracranial pressure gradually returns to the normal range, and the implanted titanium mesh graft can protect brain tissue from swings caused by atmospheric pressure or gravity [4]. In addition, DBFR itself does not induce new neurological dysfunction. We can say that the most important surgical indication of DBFR is osteopetrosis.

Historical Background

The procedure of DC was first described by Kocher in the treatment of TBI by removal of an area of the skull to expand the potential cranial volume. In the following years, from the lesson learned watching Kocher in Bern, US neurosurgeon Cushing proposed DC for the treatment of other brain disorders [5, 6]. Cushing's indication for decompressive craniectomy by aggressive wound debridement of penetrating parts Brain damage after observing 250 cases in war World I [7]. In 1976, the experience of Cooper et al. seemed to establish the end of DC as a standard practice to limit intracranial hypertension linked to the cerebral edema. He reported a 10% total and a 4% functional survival rate in 50 patients with TBI. In 1999, Guerra et al. conducted a prospective clinical study on the effect of bilateral or front temporal craniectomy in patient with refractory intracranial hypertension not responsive to medical therapy. In summary, at the end of the 20th century, the indications for DC were the following: ICP > 30–35 mmHg or cerebral perfusion pressure (CPP) < 45– 70 mmHg, age < 50 years, GCS > 4, CT signs of brain swelling, associated masses, GCS 3 plus bilateral fixed pupils excluded [8]. DC is a life-saving procedure [9, 10]. which may also lead to a series of complications because of the pathological and physiological changes induced by removing the cranium bone flap [3]. For example, skull defect, subdural hygroma, hydrocephalus, cortical herniation, paradoxical herniation, encephalocele, and seizures [11]. So, whether or not to remove the cranium bone flap is controversial. In some cases, removing the bone flap could be overtreatment. After cranium bone flap removal, the secondary cranioplasty can ensure an adequate biomechanical protection for the underlying brain, keep stable intracranial pressure, and re-establish cerebrospinal fluid dynamics and cerebral blood flow [12, 13]. Cranioplasty presentations cosmetic and protective benefits for patients after the procedure of DC and contributes to the improvement of neurological functions [14].

The necessity of performing cranioplasty in the same surgical session in a patient who has undergone decompressive craniectomy is a very rare need. The important indication for this condition is osteopetrosis. Osteopetrosis is a hereditary pathology that is rarely encountered in neurosurgery practice and affects the cranium. It presents with increased bone density due to dysfunction of osteoclasts. The biological explanation of the pathogenesis is attributed to the dysregulated ATPase pump activity. Dysfunction of chloride channels, transmembrane proteins, and carbonic anhydrases lead to deficient cell polarization, resulting in a lack of hydrochloric acid production and dysfunction of osteoclasts [15]. Although it is generally known as bone disease, the most serious and dramatic results are seen in the central nervous system. The disease results in increased intracranial pressure due to abnormal bone growth and various symptoms related to pinched cranial nerves, vascular structures, and neuronal structures in the narrowed skull base foramen [16, 17]. No definitive treatment of the disease has yet been found.

Clinical Presentation

Osteopetrosis is an inherited disorder that results from abnormal development of bone and excessive increase in density as a result of decreased activity of osteoclasts. It was first described by Albers-Schönberg in 1904 [18,19].  In the clinic, macrocephaly due to abnormal bone formation, recurrent pathological bone fractures, anemia, hepatosplenomegaly due to extramedullary hematopoiesis, susceptibility to infections and neurological findings can be present [20]. Narrowing of the neural foramen due to the increase in bone tissue may result in neurological symptoms such as hydrocephalus, hearing loss, vision loss, headache, and compression of large vascular structures [19].  It is divided into two forms as autosomal dominant osteopetrosis, and autosomal recessive osteopetrosis. Autosomal dominant osteopetrosis occurs in approximately 1 in 20,000 births [21]. There is usually recurrent persistent headache and accompanying evidence of papilledema supporting increased intracranial pressure at the base of the eye [4]. 

Diagnosis

The disease usually remains asymptomatic and is diagnosed incidentally. Symptoms are observed in late childhood and adulthood. Occurring in approximately 1 in 200,000-300,000 births, autosomal recessive form has a poor prognosis and is also known as the infantile form [21].  The diagnosis of osteopetrosis is usually made with the combination of progressive clinical and radiological findings. Cranial computed tomography (CT) imaging revealed thickening of all cranial bones and decreased intracranial volume. Cranial magnetic resonance imaging (MR) revealed that the lateral ventricles were depressed, the subarachnoid spaces were narrowed, the bilateral temporal lobe uncus was closer to the tentorium, and there was compression in the brain parenchyma in both cerebral hemispheres. Bilateral eye fundus examination should be performed. Presence of grade 1 or 2 papilledema proves increased intracranial pressure. In addition, the patient may often have hearing loss. Hearing tests may also be done.

Management

A multidisciplinary approach is absolutely necessary in the follow-up and treatment of clinically symptomatic osteopetrosis cases [17].  Acetazolamide is known as an alternative in medical treatment in cases with increased intracranial pressure. However, it is usually not sufficient. Decompressive craniectomy (DC) plays a significant role in treating refractory intracranial hypertension [3].  Neuronal decompression should be considered in symptomatic cases with insufficient response to medical treatment as well as severe calvarial and foraminal stenosis [17]. 

Al-Meftyet al mentioned visual recovery after optic nerve decompression with the supraorbital bilateral approach in 5 of 6 patients with osteopetrosis in 1988 [22].  Jeong-Min Hwang et al shared the results of visual recovery after optic nerve decompression in their case report and underlined the importance of visual findings in the follow-up and management of osteopetrosis [23].  In our patient, visual complaints improved after unilateral decompressive cranioplasty without optic nerve decompression. We believe that the improvement in visual complaints is due to the decreased ICP after decompression.

In the literature, no patient with a diagnosis of osteopetrosis, who had previously undergone suboccipital decompression, had both unilateral decompressive craniectomy to reduce intracranial pressure and cranioplasty with a titanium mesh to protect the cerebral tissue in the same session has not been identified. It has been observed that there is no clear decision in the literature indicating the most appropriate cranioplasty material for these patients. The surgical technique steps and the patient's follow-up findings are presented in the light of the literature.

The operation for both cerebral decompression and cranioplasty in the same session in a patient whose intracranial pressure increase is a very rare decision in neurosurgery practice. According to a study published in 2017, Allahsawi et al. used thinned autologous bone as cranioplasty material after cranial decompression in a case of osteopetrosis presenting with decreased visual acuity, coughing, and sneezing, and progressively increasing headache [4].  Although autogenous grafts, allogeneic implants, or alloplastic materials can be used for the reconstruction of craniofacial defects, the most appropriate material is still controversial [4]. The aim of decompression in osteopetrosis patients should be to provide more volume to the neuronal tissue. In this case, considering that the young age of the patient may cause bone re-growth due to osteopetrosis and eventually the re-occurrence of symptoms as the result of increased intracranial pressure, titanium mesh was preferred. This preference is supported by the results obtained in the study of Junhua Ye et al [4]. 

The surgical techniques and results for decompression in patients with osteopetrosis are presented in Table 1 [4, 16, 24–30]. Titanium mesh has been increasingly used in reconstructive surgery in recent years due to its many advantages including ease of application, the possibility of personalized peroperative three-dimensional reconstruction, suitability for radiological imaging, and low infection rates [8]. In our study, the titanium mesh was easily shaped in accordance with the anatomy and fixed to the cranium with a miniplate screw. In this way, both a wider area and a solid cover have been provided to the neuronal tissue. ICP has decreased with the increase of intracranial volume (Figure 3). Another advantage of using titanium mesh instead of thinning cranial bone is elimination the risk of re-operation due to bone development.

Prognosis and outcome 

In patients with symptomatic osteopetrosis, cranioplasty can be considered as an option to reduce increased ICP and it is reported that their complaints decreased of the cranial nerve palsies together [4].   

Exemplary Case description

A 24-year-old female patient with a diagnosis of osteopetrosis underwent suboccipital decompression due tosevere headaches as a result of Chiari malformation seven years ago. She admitted to our outpatient clinic with complaints of headaches especially provoked by coughing and sneezing, aggressive personality changes, and loss of vision and hearing over the past year. There was an increase in the complaints of nausea and dizziness. No motor defects were reported in the extremities in the neurological examination. Cranial nerves were evaluated. A decrease in visual acuity was detected. Finger counting from approximately 5 meters was decreased in both eyes. An ophthalmological examination was performed. Bilateral first-degree papilledema was detected. In Puretone audiometry, mild hearing loss was detected with an average of 32 dB in both ears.  Pseudo-meningocele appearance, which is a sign of increased ICP, was observed in the posterior wall of the posterior fossa, especially in the area of previous suboccipital decompression (Figure 1). Abnormal bone growth due to osteopetrosis has resulted in the growth of the calvarium and decreased cranial volume, and eventually presented with clinical manifestations due to increased intracranial pressure. In our patient, bilateral decompressive cranioplasty was considered in the first place, but due to the cranial thickness ranging from 2.2-3.1 cm, we first decided to perform the surgery unilaterally to see the clinical results. It was decided to perform right-sided temporoparietal decompressive cranioplasty due to the left dominant hemisphere. Our patient underwent unilateral decompressive cranioplasty by using titanium mesh. The dura was not opened considering the risk of herniation to the outside. The sphenoid wing on the proximal of the Silvian Sulcus was thoroughly defeated with high-speed Dril. No intraoperative complications were encountered. Rapid improvement in clinical symptoms was observed in the early postoperative period.

Surgical Approach

After surgical sterilization, in the supine position with the head turned 45 degrees to the left under general anesthesia, a right-sided wide pterional incision was performed to access the skull base. After controlling the bleeding with bipolar cautery, the temporal muscle was hung by opening the base in accordance with the procedure.Four Bure Holes, 2 on the base of the temporal bone and 2 on the anterior and posterior parts of the parietal bones, were carefully opened with the help of a high-speed drill. Since the cranium was extremely hard and its thickness was approximately 2.6 cm, continuous irrigation of the drill bit with saline was required, which overheated during the procedure. Each Burr Hole took about 20-25 minutes to open. The bone flap was released with difficulty after the bone surface between the opened burrholes was drilled and adjusted to the depth of the cutting attachment.150 cc of mannitol was injected by slow infusion without lifting the flap. There was no dural adhesion (Figure 2A and B). The opening time of the cranium exceeded 2 hours as a result of the utmost care to avoid complications due to bone hardness and thickness. Sphenoid wing drilled and excised by Kerrison Rongeur Considering the risk of cerebral herniation and cortical damage due to increased intracranial pressure, duraplasty was not performed. Dura membrane was not opened. The titanium mesh was fixed to the intact bone using eight mini-plate screws to cover the craniectomy area and cranioplasty was performed. The temporal muscle was attached by stretching on titanium (Figure 2C and D). Hemovac drain was placed on titanium mesh in the surgical field after the control of the bleeding has established. The distal end of the temporal muscle was suspended on the titanium mesh. The layers were closed in accordance with the anatomy. There were no complications. Hemovac drain was kept for 2 days.

Postoperative follow-up and Outcomes   

There was no problem in the wound care of the patient. At the end of 2 weeks, the stitches were removed. At the end of the 4th month of the patient, there was a punctual opening at the incision site.  The relationship between titanium and cranium was evaluated by computerized tomography. It was understood that the cause of the problem was the tension in the scalp due to the chronic enlargement of the cranium. Even though the titanium was thin and was attached to the bone under the skin with mini screws from multiple points, it created a slight tension on the skin. The strain was increased. A suitable skin flap was planned for the patient and z-plasty was performed by dr koksal (figure 4). The tension in the skin has spread to other areas. Thus healing occurred in the scalp. At the end of approximately 2 years of follow-up, the patient's wound was completely healed and she had no neurological complaints.

Conclusions

We believe that titanium mesh is the most suitable material for performing cranioplasty in the same session together with decompressive craniectomy in order to protect neuronal tissue and increase the intracranial space in symptomatic patients with osteopetrosis. It was also understood that not opening the dura during the surgical procedure did not change the result, but contributed to the protection of the brain tissue. Unilateral cranial decompression permanently improved the symptoms of personality change, agitation, and chronic severe headache.

Declarations

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflicts of interest/Competing interests

The authors have no conflict of interest to declare.

Availability of data and material

All data is available online

Ethics approval

All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standard.

Consent to participate

Written informed consent was obtained from the patient for publishing this article accompanied by the MRI images.

Patient consent

The patient consented to the submission of this case report to a medical
 journal.

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Table

Table 1 is available in the Supplementary Files section