Cavernous malformations (CM) or cavernomas of the central nervous system are formations consisting of multiple adjacent cavities of irregular shape (caverns), lined with endothelium and filled with blood.

According to magnetic resonance imaging (MRI) data at the screening stage and several thousand autopsies, CM of the central nervous system is detected in 0.3–0.6% of the population [1][2]. Most often, the first symptoms appear at a young age – on average, at 23 years [3].

Of all CMs of the brain, localization in the brainstem accounts for 19 to 30% [3], of which 14.2–25% occur in the midbrain [4]. In cerebral CMs, the annual frequency of primary hemorrhages is 0.39-1.3%, recurrent – 4.5–22.9% [5]. It is believed that brain cavernomas located in the brainstem area are most prone to recurrent hemorrhages with an annual risk ranging from 21–60% and complications during surgical intervention than with other localizations of cavernomas [6–9]. The risk of recurrent bleeding increases with incomplete surgical resection [9][10]. These features allow to distinguish brainstem CMs into a separate group.

The tactics of surgical treatment of primary bleeding from the midbrain CM depend on the timing of the hemorrhage, age and somatic status of the patient and necessitate an individual approach to developing an optimal treatment strategy.

The purpose of this case report is to demonstrate the experience of successful radical resection of the midbrain peduncle CM by the supracerebellar infratentorial approach as an effective surgical strategy for primary hemorrhage in a young patient.

A 38-year-old man, a builder, sought medical help at the SI “National Medical Center of the Republic of Tajikistan Shifobakhsh” on May 13, 2024 with complaints of diplopia and mild weakness in the right limbs, which arose suddenly after an episode of headache and vomiting about two weeks previously.

Clinical examination on admission: clear consciousness, 15 points according to the Glasgow Coma Scale, somatic status without any peculiarities: respiratory rate 16 per minute, heart rate 80 per minute, blood pressure 120/80 mm Hg. In the neurological status, a slight decrease in strength on the right side was noted – IV/V degree according to the classification of muscle tone study1, strabismus downward and outward, mild mydriasis and paralysis of accommodation of the left eye alongside alternating syndrome.

Computed tomography (CT) of the brain revealed a poorly defined hyperdense formation in the lower part of the dorsal surface of the left peduncle of the midbrain measuring 20x30x25 mm. MRI of the brain revealed a hyperintense lesion in T1- and T2-weighted images with a clearly defined hypointense rim, hematomas in a cavernoma of 20×30×25 mm (Fig. 1A–C).

Based on clinical data and neuroimaging results, the following diagnosis was made: rupture of CM of the left midbrain peduncle, hematomas in the cavernoma.

To avoid any postoperative neurological deficit (as assessed by additional scales: 4 points on the Spetzler–Martin [11] and 3 points on the Lawton–Young [12]), a median suboccipital craniotomy with a contralateral supracerebellar infratentorial approach was chosen for radical cavernoma resection (Fig. 2A–E).

The operation was performed on May 28, 2024 under general endotracheal anesthesia with the patient in a sitting position – to give the back a vertical position, and with the head tilted forward to smooth the angle of the tentorium. The patient’s head was rigidly fixed using a Mayfield-Keys clamp. The Carl Zeiss OPMI Vario S88 operating microscope (Carl Zeiss, Germany) was used during the operation.

Surgical access was achieved through a 12 cm long linear skin incision in the parietal-occipital region. A burr hole was created in the occipital protuberance region, which provided a circular craniotomy measuring 80x60 mm with exposure of the sinus drain and contralateral supracerebellar infratentorial access with gravitational retraction of the cerebellum. The upper edge of the bone flap was located on the transverse sinus.

A semi-oval incision of the dura mater, reinforced with interrupted sutures, was made, which elevated the transverse sinuses and provided entry into the supracerebellar infratentorial plane. The sagging of the cerebellum widened the natural corridor to the quadrigeminal cistern. Cerebrospinal fluid was drained from the cisterna magna, and the cerebellum was retracted by dissection of the arachnoid adhesions connecting the posterior superior border of the cerebellum to the outer edge of the tentorium. To access the free edge of the tentorium, the bridging veins between the cerebellum and the tentorium were divided. The arachnoid membrane dissection of the posterior edge of the quadrigeminal cistern was performed to visualize the dorsal part of the midbrain.

The supracerebellar infratentorial approach in the sitting position opens the anatomical plane so widely that dissection is significantly facilitated. Any discomfort from working with raised arms is compensated by the panorama without a retractor and the operative field cleared by gravity (Fig. 3A). Arachnoid dissection was performed, and large deep veins (V. Galen, internal cerebral veins, internal occipital veins, basal veins of Rosenthal, pericentral veins of the cerebellum) were identified. The contralateral approach allowed visualization of the IV pair of cranial nerves and the P3 segment of the posterior cerebral artery.

With a minimal incision in the dorsal part of the midbrain (Fig. 3B), the cavernoma was completely resected together with the surrounding subacute hematoma measuring 2×3×2.5 cm (Fig. 3C). Hemostasis was achieved until the lavage water was clear. A hemostatic collagen sponge was placed in the cavernoma bed. The dura mater was sutured hermetically. The bone flap was fixed with threads. Layer-by-layer suturing of the wound was performed. An aseptic dressing was applied. The total blood loss was 250 ml.

A control CT scan in the postoperative period was performed on the third day; according to the study data, the condition after median suboccipital craniotomy, residual cavernoma, and repeated hemorrhage were not detected (Fig. 4A, B).

In the postoperative period, the patient’s consciousness is clear (15 points on the Glasgow Coma Scale), diplopia and moderate pyramidal disorders disappeared on the 12th day. The course of the postoperative period is smooth, without the development of postoperative complications. The patient was discharged from the hospital on the 15th day after the surgical intervention.

The patient came for a follow-up examination and assessment of the long-term treatment results on February 18, 2025. During the examination, the patient’s consciousness was clear. No sensory or motor disturbances were observed after the surgery. He was able to walk and take care of himself independently. The patient has fully recovered and returned to professional activities without any restrictions.

A MRI of the brain was undertaken on February 18, 2025, and here we can observe the brain’s condition after removal of the cavernoma. The MR showed signs of postoperative gliosis changes. No residual cavernoma or recurrent hemorrhage was detected (Fig. 5A, B).

At present, one of the main issues in treating midbrain CM is determining the timing of the surgical intervention, be it in the acute or the subacute period.

In our case, the patient was operated on the 20th day after the primary hemorrhage. The cavernoma was located in the subacute hematoma, which made it easy to remove together with the cavernoma itself.

According to generally accepted practice and in line with our clinical experience, surgical treatment in the subacute stage of hemorrhage, when the hematoma is liquefied, is effective for maximum removal of the hematoma with minimal incision of the brainstem [13]. In such cases, a limited incision of the brainstem contributes to the most complete neurological recovery.

The next question concerns the choice of tactics for a safe approach to the midbrain area.

Dorsal lesions are localized in the zones of two thin horizontal lines immediately above and below the quadrigeminal plate. For their surgical treatment, supratentorial suboccipital, occipital transtentorial, supracerebellar infratentorial, posterior subtemporal and tonsillouveal transaqueductal approaches are used [14].

In the presented case, the infratentorial approach to the posterior fossa was used to remove the midbrain CM – this method is most often used by leading neurosurgeons around the world such as M. Lawton and R. Spetzler [3–5]. The two principal craniotomies were used to access the posterior fossa: retrosigmoid (lateral suboccipital) craniotomy and medial suboccipital craniotomy. The retrosigmoid supracrebellar approach was used to reach the lateral midbrain. The medial suboccipital supracrebellar approach was used to reach the dorsal part of the midbrain and the quadrigeminal plate [15].

The surgical tactics used in the subacute period of hemorrhage from the cavernoma allowed for radical removal of the midbrain CM, ensuring complete neurological recovery of the patient. The patient was able to carry on with his work as usual and there were no signs of a reoccurring hemorrhage (the observation time was 6.5 months).

Knowledge of the brainstem corridors is necessary for planning microsurgical interventions on brainstem formations so as to minimize the risk of damage to nearby structures.

The subacute phase of midbrain CM bleeding may be the best time for surgical resection of the cavernoma. The contralateral supracerebellar infratentorial approach is one of the available options for resection of dorsal midbrain CM. It can be considered if the formation is located behind the cerebral peduncle, facing the intrapeduncular fossa and interpeduncular cistern and extends to the dorsal side.

Narzullo O. Rahimov and Khurshed J. Rakhmonov performed surgical treatment and developed the concept of scientific work. Dzhumaboy R. Sanginov, Mahmarajab A. Khasanov developed the methodology for selecting and describing CT and MRI images. Narzullo O. Rahimov collected the material and analyzed the literature data. All authors approved the final version of the publication.

Compliance with ethical standards. Consent statement. The patient consented to the publication of the article “Microsurgical removal of a cavernous malformation on the midbrain dorsal surface using the supracerebellar infratentorial approach: а clinical case” in the “Sechenov Medical Journal”.

Conflict of interests. The authors declare that there is no conflict of interest.

Financing. The study was not sponsored (own resources).

1. Index of Clinical Guidelines by the Russian Ministry of Health / Clinical Guidelines / Mononeuropathies (Approved by the Ministry of Health of the Russian Federation) https://cr.minzdrav.gov.ru/preview-cr/166_2 (access date: 13.05.2024).