Introduction
In the intricate realm of neurosurgery, cranioplasty stands as a crucial procedure addressing both structural and aesthetic aspects, but it can introduce a spectrum of potential postoperative complications. This article presents an unusual case of bilateral 6th nerve palsy resulting from intracranial hypertension immediately following methyl methacrylate (MMA) cranioplasty performed after the surgical resection of Ewing’s sarcoma in the occipital bone of a 21-year-old woman.
Case report
A 21-year-old woman presented with a swelling in the occipital region that had been gradually increasing in size for the past year. There was no pain or associated general symptoms; rather, the patient sought medical attention due to cosmetic discomfort. Angio scanning revealed a large extracranial, isodense mass with malignant features measuring 12.5 × 7.5 × 9.5 cm. The mass was vascularized, associated with erosion of the occipital bone, and showed no intracranial extension (Fig. 1).
The patient underwent surgical excision of the tumor, with resection of the eroded occipital bone. There was no involvement of the internal aspect of the occipital bone or invasion of the underlying dura mater. Subsequently, a cranioplasty with polymethyl methacrylate was performed. Pathological examination of the operative specimen identified Ewing’s sarcoma. Additional radio-chemotherapy was decided upon.
The patient experienced headaches, visual blurring, and diplopia in the immediate postoperative period. Ophthalmological examination revealed, in both eyes, a visual acuity of 9/10, normal anterior segments, and an intraocular pressure of 14 mm Hg. Fundoscopic examination demonstrated bilaterally symmetrical swollen optic discs with blurred margins, without haemorrhages or exudates suggestive of papilledema (Fig. 2). The ocular motility was restricted in the external gaze in both eyes. The Lancaster test revealed a limitation of the external rectus muscles and hyperaction of the internal rectus muscles (Fig. 3).
Computed tomography and magnetic resonance imaging showed inflammatory changes at the cranioplasty site, ruling out intracranial involvement or cerebral thrombophlebitis (Fig. 4). Lumbar puncture indicated an opening pressure of 35 cm H2O with normal cerebrospinal fluid composition. The diagnosis of intracranial hypertension secondary to cranioplasty was established. The patient was treated with acetazolamide 3 g/day and potassium supplementation, resulting in a good functional recovery (Fig. 5).
Discussion
Ewing sarcoma, with an incidence of 2%, stands as one of the most dreadful cancers. While it could concern people of all ages, it mainly affects children. It is a malignant tumor that primarily emerges in bones but could also manifest within soft tissues. It is ranked as the second most prevalent bone cancer in the paediatric population [1]. Management of this rare disease involves a multidisciplinary approach, including surgical resection and radiotherapy, and may as well be associated with chemotherapy [2].
Skull bones metastatic Ewing’s sarcoma is seen frequently, but primary Ewing rarely involves the cranium [3]. This specific location accounts for only 1% of all cases. It affects predominantly the temporal bone, with the parietal bone and occipital bone being the subsequent most frequently involved sites [4].
Only a few cases of occipital bone involvement in primary Ewing sarcoma have been reported in the literature. In contrast to our patient, who exhibited only swelling of the posterior cranium, all documented cases reported severe headaches. Management of Occipital Ewing sarcoma involves a combination of cytotoxic drugs and surgical reduction or radiotherapy, or both [1]. Cranioplasty after resection of the tumor can be performed using various techniques and materials, such as an allogenic or autologous bone graft or an endoprosthesis. Methyl Methacrylate (MMA) is commonly employed as a cranioplastic material due to its widespread availability and cost-effectiveness [5].
In all the series where MMA has been used, there were mainly no severe post-operative complications described. In 1985, Vangool conducted a descriptive study that included 45 patients who had undergone MMA cranioplasty. No complications were reported related to the prosthesis, such as infection or disturbed wound healing [6].
Counting the side effects of MMA described in the literature, one could only mention those stated by Azmi et al., where 26.5% of all the patients included presented with a headache after surgery, but 85% of the patients improved after two months of proper treatment. The remaining patients required regular medication. Only one patient of the series experienced an exacerbation of headaches accompanied by vomiting in the immediate post-operative period but fully recovered within one month [5].
To date, there have been no documented cases where MMA cranioplasty has resulted in a complication such as intracranial hypertension (IH), as it was described in our patient.
Considering the definition of idiopathic intracranial hypertension (IIH), our case meets the predefined criteria of the disease [7]. Thus, it cannot be classified as such, given the clinical context in which the symptoms occurred. Only conjectures may be put forward as a possible remedy to the pathophysiological mechanism behind our patient’s condition, which could be similar to that of IIH.
The pathophysiology of IIH is admittedly quite complex, invoking the restriction of venous drainage pathways, congestion of the glymphatic system, and blockage of the cerebrospinal fluid (CSF) lymphatic drainage pathway. CSF loaded with brain parenchyma waste would be eliminated in part via lymphatic vessels present in the dura mater [8]. The same pathophysiological model can be used to explain the clinic of our case.
Hence, it is plausible that the heat produced through the auto-polymerization of methyl methacrylate during its preparation could induce thermal damage to the underlying brain, given its exothermic reaction [5]. This could potentially result in congestion of the underlying venous circulation. The origin of this hypertension could be attributed to the waste product of MMA circulating in the cerebrospinal fluid, which is eliminated through the lymphatic vessels described earlier.
The symptoms in our patient exclusively emerged after the surgical intervention, aligning with those characteristics of IIH. This latter typically exhibits signs such as papilledema, headache, pulsatile tinnitus, and transient visual obscuration. In 20% of cases, patients may also present with horizontal binocular diplopia in cases of abducens nerve (VI) paralysis [7].
The VI cranial nerve (CN) palsy has previously been described in IIH among children. Findings of an American study in 2015 suggest an incidence of CN VI palsy in paediatric IH patients of approximately 12%. Furthermore, papilledema was an associated finding, which resolved ultimately after treatment [9]. Observations that were concurrent with our case.
Conclusion
This unique case challenges existing literature, as intracranial hypertension after MMA cranioplasty has not been previously documented. The pathophysiological mechanism is hypothesized to involve thermal damage from the exothermic reaction during MMA preparation, leading to venous congestion and interference with cerebrospinal fluid drainage. The manifestation of symptoms aligns with idiopathic intracranial hypertension (IIH) characteristics, emphasizing the need for careful consideration of complications associated with cranioplasty materials. This case contributes to our understanding of rare postoperative complications and underscores the importance of tailored treatment approaches for optimal patient outcomes.
Conflicts of interest
The authors declare that there is no conflict of interest regarding the publication of this paper.
Author contributions
T.A: patient care and follow-up, bibliographic research, and writing of the manuscript; S.S.: bibliographic research, and writing of the manuscript; M.Y.: bibliographic research, supervision and correction; O.A.: bibliographic research, supervision and correction.
Acknowledgments
None.
Funding
None declared.