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Cavernous malformation of the optic nerve: clinical case and literature review
Journal: Burdenko's Journal of Neurosurgery. 2020;84(1): 62‑68
Read: 3502 times
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Abbreviations
CM — cavernous malformation
CNS — central nervous system
ON — optic nerve
MRI — magnetic resonance imaging
Cavernous malformation of the optic tract is a rare pathology accounting for approximately 1% of all cavernomas of CNS [1]. The first report of CM of the optic nerve was described by Klein et al. in 1979 [2].
The disease is usually manifested by the so-called "chiasmal apoplexy" including acute visual disturbances, headache and retroorbital pain, nausea [3]. Transient visual impairment and moderate headache often precede paroxysmal symptoms for several weeks or months.
Symptoms may be persistent without progression. However, irreversible damage to the optic nerves may occur due to hemorrhage in some patients.
Surgical treatment of CM is performed for optic nerve decompression and prevention of repeated hemorrhage. The choice of approach is based on CM dimension and localization, neuroimaging data and clinical symptoms. Pterional, lateral supraorbital, supraorbital transbrow approaches are traditionally used [4—8]. Total resection of CM is the main objective of microsurgical treatment. Partial resection may be followed by recurrent hemorrhages with subsequent visual impairment [9, 10].
We report clinical example of resection of CM of the left optic nerve.
Case report
A 32-year-old patient K. turned to neurosurgical department with complaints of recurrent headaches and impaired vision in the left eye.
Analysis of anamnestic data revealed that periodic headaches with subsequent acute visual impairment in the left eye occurred 2 weeks prior to admission. Outpatient MRI of the brain revealed neoplasm of the left optic nerve. The patient appealed for surgical treatment.
According to MRI data, there was neoplasm of the left optic nerve 9.5x11.1 mm in the intracranial segment with increased MR signal in T2 and DWI images. Tumor was characterized by rounded shape, clear contours and no contrast enhancement (Fig. 1a—c).
Differential diagnosis included saccular aneurysm of the left internal carotid artery considering shape, localization, dimensions of the neoplasm and its relationship with optic nerve. However, CT angiography did not reveal vascular aneurysm (Fig. 1d).
Ophthalmological examination confirmed visual impairment in the left eye up to 0.3 and right-sided hemianopsia with predominant visual field loss in the left eye. Refraction of both eyes was similar. There were no oculomotor disorders. Optic nerve disc was pale pink with clear boundaries and no edema.
Microsurgical resection of CM through lateral supraorbital approach was preferred considering complaints, anamnestic data, clinical symptoms and MRI data.
Сraniotomy was followed by dissection of dura mater and exposure of basal cisterns for brain relaxation. We did not apply fixed traction of the frontal lobe. Enlarged yellow left optic nerve with reduced vascular pattern was visualized. Cherry-colored focal lesion resembling cavernoma with signs of hemorrhage and nerve compression was visualized under pial sheath of the nerve. Dissection of arachnoid adhesions was not followed by adequate mobilization of the nerve and evaluation was difficult. Partial resection of the upper wall of the optic canal was performed for optic nerve decompression and improvement of visualization. There were hemorrhagic foci with dense blood clots and small number of homogeneous brownish-reddish semi-liquid masses in subacute-chronic stage. These masses were easily separated from the optic nerve. Decompression was followed by complete dissection of the neoplasm with subsequent histological examination. The wound was closed in layer-by-layer fashion, bone flap was fixed with titanium mini-plates. Skin incision was sutured using continuous intradermal suture. No drainage was used. There were no complications. Stages of resection are shown in Fig. 2.
Length of ICU-stay was 1 day. Control CT of the brain did not reveal any complications (Fig. 3).
The patient was activated on the first postoperative day. Ophthalmological examination on the 4th day revealed mild impairment of visual acuity up to 0.25 and slight enlargement of visual field loss on the left. The patient was discharged on the 5th day. Morphological examination revealed blood clots with signs of organization, neoplasm wall was represented by connective tissue and small foci of hemorrhage. Morphological diagnosis is cavernous malformation.
Follow-up examination in 3 months after surgery confirmed recovery of visual acuity on the left up to 0.3 and regression of hemianopsia. Control MRI of the brain revealed postoperative changes of the left optic nerve. There were no data on recurrent hemorrhages and cavernous lesion (Fig. 4).
Prevalence of CM of cranial nerves is quite small. Lesions of the cranial nerves II—V and VII—VIII are reported in the literature [5, 11]. To date, there are about 50 reports of CM of the visual tracts [12, 13].
In most cases, clinical symptoms appear in 2—4 decades of life [14]. As a rule, there is no correlation of CM with gender. However, there are data on predominant hemorrhages from CM in women [15]. Visual disturbances prevail as clinical symptoms of CM of the optic nerve. "Chiasmal apoplexy" is due to hemorrhage inside the CM [16]. According to the literature, annual incidence of hemorrhages is 0.7—3.1% [14, 17]. Primary hemorrhage increases the risk of subsequent hemorrhages. However, the risk is gradually decreased 2—3 years later [18]. There are no clear statistical data on the incidence of hemorrhages in patients with CM of the optic tract. Nevertheless, it is believed that the risk is higher than for other parts of central nervous system [19, 20].
MRI is preferred for diagnosis of CM. Neuroimaging characteristics of optic CM are similar to CM of the other parts of central nervous system [19, 21, 22]. Differential CT diagnosis of optic CM should include tumor and thrombosed aneurysm since hyperintense foci and possible calcifications may be observed in patients with above-mentioned pathology too [23]. Cerebral angiography makes it possible to exclude abnormal vessels of arteriovenous malformation. However, venous angiomas may be also diagnosed in patients with verified CM [1, 24].
Moreover, differential diagnosis is made with gliomas and meningiomas of the optic nerves, craniopharyngiomas (contrast agent accumulation is typical), pituitary apoplexy, optic nerve neurinoma [25—30].
According to various authors, microsurgical treatment is preferred for optic nerve CM. Total resection of CM is the only method to prevent recurrent hemorrhages, since any residual part of CM may be a source of repeated hemorrhages [5, 6, 19—21].
Early surgery is indicated for optic nerve CM in most cases [5, 6, 21]. Diagnosis followed by surgery within 24 hours after clinical manifestation is preferred in patients with "chiasmal apoplexy" for rapid decompression of visual pathways [19]. Timely diagnosis is essential since even complete loss of vision may be reversible in case of fast decompression of the optic nerves [31].
The main features of microsurgical stage are resection of optic canal roof for mobilization and decompression of the nerve, incision of the pial membrane of the nerve with longitudinal dissection, resection of CM. This approach is advisable to correct visual impairment.
Stereotactic radiosurgery is effective for hemispheric and brainstem CM. However, the use of this technique for CM of anterior optic tract is associated with increased risk of irradiation-induced optic neuropathy [32].
Liu et al. reported the largest sample of 65 patients with CM in the optic tract and hypothalamus. Complete resection of CM was carried out in 60% of cases, subtotal resection — in 4 patients (6%), biopsy — in 4 patients (6%), biopsy with visual tract decompression — in 15 cases (23%). Vision improvement was noted in 75% of patients, postoperative deterioration occurred in 2 (4%) patients. Any changes were absent in 19.3% of cases. Conservative approach was applied in 2 patients (vision improvement and deterioration in each case, respectively). Radiosurgery was used in 1 case without significant positive effect for visual functions [12].
Shkarubo A.N. reported chiasmal cavernoma in a 23-year-old patient with visual disturbances associated with endocrine disorders (polyuria, polydipsia). Therefore, differential diagnosis was made between craniopharyngioma and chiasmal glioma. Resection of hematoma capsule and debridement of blood clots were performed. Cavernous malformation was histologically confirmed [33].
Grigoryan Yu. A. et al. reported another case of intrachiasmal hematoma. There was “chiasmal apoplexy" in a 41-year-old patient. Resection of chiasmal hematoma was performed through pterional approach. The authors analyzed literature data on the features of diagnosis and treatment of intrachiasmal hemorrhages [34].
CM of the optic nerves is rare disease characterized by difficult diagnosis and microsurgical treatment. Early surgery is preferred for “chiasmal apoplexy". Total resection of CM may be followed by improvement of visual function.
Authors’ participation:
Concept and design of the study — R.S., O.N., V.A.
Collection and analysis of data — R.S., A.V., E.I.
Statistical analysis — A.V., R.L.
Writing the text — R.S., A.V.
Editing — V.A., O.N.
The authors declare no conflicts of interest.
The authors discuss differential diagnosis of focal lesion of chiasmal-sellar zone. This is very important issue despite the authors report only single clinical observation. Erroneous preliminary diagnosis does not affect the choice of surgical approach in some cases. However, intraoperative finding of this lesion can confuse even a fairly experienced surgeon.
Undoubtedly, timely diagnosis is crucial. Neurological, ophthalmological examination and early MRI are essential for effective treatment. At the same time, the quality of examination is also of great importance in these cases. It should be remembered that SWAN sequence is obligatory diagnostic approach in these patients.
The authors comprehensively describe surgical technique and emphasize great importance of adequate mobilization of the optic nerve. It is worth adding here that resection without optic nerve decompression or advanced decompression with clinoidectomy may be performed depending on certain situation (including spread of CM).
Incidence of this disease is small, but knowledge of preoperative picture and surgical technique will significantly improve clinical outcomes in these patients. Therefore, this report is very useful for neurosurgeons
V.A. Cherekaev, N.V. Lasunin (Moscow, Russia)
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