Abstract

BackgroundTraumatic posterior inferior cerebellar artery (PICA) aneurysms are rare. Fractures of the occipital condyles (OCs) have been reported to cause delayed hypoglossal nerve (HN) palsy possibly.

Case DescriptionA 67-year-old man fell while hiking on a mountain. On initial presentation at a local hospital, the patient exhibited right abducens nerve palsy and hoarseness. Cranial computed tomography (CT) revealed multiple intracranial air densities, with no remarkable hemorrhages detected in the cerebral cisterns. In addition, fractures involving both the OCs and clivus were identified, along with a collapsed left hypoglossal canal. Three days later, the patient developed a severe headache and coma. CT showed an extensive subarachnoid hemorrhage in the perimedullary and basal cisterns. After conservative management, the patient was transferred to our hospital. On examination, no instability in the craniocervical region was found; however, marked atrophy was noted in the left tongue. Cerebral angiography revealed a fusiform aneurysm in the proximal PICA. Stent-assisted coil embolization was successfully performed. The patient was eventually transferred to a rehabilitation facility.

ConclusionTraumatic PICA aneurysms may be complicated by HN palsy. A thorough evaluation with clinical and radiological examinations is essential for correct diagnosis and appropriate treatment.

Keywords: Fall, Hypoglossal nerve palsy, Mountain hiking, Traumatic posterior inferior cerebellar artery aneurysm

INTRODUCTION

Mountain hiking has continued to increase in popularity. With more participants, the number of injuries is likely to increase.[ 2 ] Victims of non-fatal falls during mountain hiking have been reported to be older than the general population of mountain hikers.[ 5 ]

Traumatic intracranial aneurysms are a distinct entity accounting for approximately 1% of all cerebral aneurysms.[ 8 ] Among them, aneurysms arising from the posterior inferior cerebellar artery (PICA) have been rarely documented.[ 8 , 9 , 12 ]

The hypoglossal nerves (HNs) are anatomically divided into five segments: cisternal, intracanalicular, descending, horizontal, and ascending.[ 7 ] The intracanalicular segment passes through the occipital condyle (OC), which forms the lowest part of the occipital bone. Although the OC shows morphological variability, it is known to be a helpful landmark during skull base surgeries and when placing the occipital condylar screw.[ 1 , 11 ] OC fractures can also result in HN palsy. These fractures are estimated to occur in 16% of all patients with craniocervical trauma.[ 10 ] These are most commonly detected in patients with severe injuries, but fractures can also occur in cases of minor head trauma and may not be easily diagnosed through routine clinical and radiological evaluations.[ 3 , 6 ] Furthermore, OC fractures can cause delayed HN palsy.[ 4 ]

Herein, we report the case of a patient who fell during mountain hiking, followed by the acute rupture of a traumatic PICA aneurysm and delayed HN palsy.

CASE PRESENTATION

A 67-year-old previously healthy man stumbled and fell during a mountain hike, falling onto the parietal region. At an initial presentation at a local hospital in the mountainous region, the patient was well oriented but presented with the right abducens nerve palsy and hoarseness. Cranial computed tomography (CT) revealed multiple air densities in the cerebellar convexity, as well as the prepontine, ambient, and basal cisterns. No significant hemorrhages were detected in the basal or prepontine cisterns [ Figure 1 ]. Bone-targeted CT revealed skull base fractures involving both the OCs and clivus, with the left hypoglossal canal collapsed and much smaller than the right [ Figure 2 ]. Three days later, the patient suddenly presented with a severe headache, followed by a disturbance in consciousness (4/15 on the Glasgow coma scale) and respiratory distress. CT showed subarachnoid hemorrhages extensively distributed over the perimedullary, prepontine, ambient, and basal cisterns, with perimedullary clots predominantly on the right side [ Figure 3 ]. Although three-dimensional CT angiography suggested an aneurysm on the right PICA, due to poorly equipped circumstances, the patient was conservatively managed. Nine days later, he was extubated but showed respiratory distress and deterioration of consciousness over the next 3 days. The patient was transferred to our hospital on the 15^th day after the identification of subarachnoid hemorrhage. On presentation, the patient was drowsy, exhibited swallowing disturbances, and showed considerable atrophy in the left half of the tongue. A tongue protrusion deviated to the left. However, no instability was observed at the craniocervical junction or cervical spine. Cerebral angiography revealed a fusiform aneurysm, measuring 4.3 mm × 3.6 mm in diameter, on the proximal segment of the right PICA. The patient underwent endovascular therapy that achieved successful stent-assisted coil embolization, maintaining the flow of the parent artery [ Figure 4 ]. Bone-targeted CT performed immediately after endovascular therapy revealed that the embolized aneurysm was located at the level of the medial edge of the hypoglossal canal [ Figure 5 ]. During the postoperative course, the patient’s lower cranial neuropathy worsened significantly over the next month with bilateral tongue atrophy. Then, a tracheostomy was performed. Constructive interference steady-state magnetic resonance imaging revealed the cisternal segment of the left HN with an abnormally tortuous course [ Figure 6 ], while the course of the right HN appeared intact. The patient was transferred to a rehabilitation facility on the 55^th post embolization day, with a modified Rankin scale score of 4.

Figure 1:

(a and b) Axial computed tomography performed 2 h after fall showing multiple air densities in the cerebellar convexity and prepontine, ambient, and basal cisterns (dashed arrows). No remarkable hemorrhages are found in the basal or prepontine cistern.

Figure 2:

(a and b): (a) Axial and (b) coronal bone-targeted computed tomography showing fractures in both occipital condyles (dashed arrow). The left hypoglossal canal is collapsed and much smaller, compared to the right counterpart (b, arrow).

Figure 3:

(a and b) Axial computed tomography performed 3 days after the fall showing subarachnoid hemorrhages extensively distributed over the perimedullary, prepontine, ambient, and basal cisterns (arrows). Perimedullary clots are dominant on the right.

Figure 4:

(a) Anteroposterior view of right vertebral angiography showing a fusiform aneurysm, 4.3 mm × 3.6 mm in diameter, on the proximal segment of the posterior inferior cerebellar artery (arrow). (b and c): Anteroposterior (b) and oblique (c) views of the right vertebral angiography at the completion of endovascular therapy, showing the embolized aneurysm (arrow) maintaining flow in the posterior inferior cerebellar artery. AICA: Anterior inferior cerebellar artery; BA: Basilar artery; PICA: Posterior inferior cerebellar artery; VA: Vertebral artery.

Figure 5:

(a and b): (a) Axial and (b) coronal bone-targeted computed tomography performed immediately after endovascular therapy showing the embolized aneurysm (dashed arrow) located at the level of the medial edge of the hypoglossal canals (arrow).

Figure 6:

(a-c) Serial images of the axial constructive interference steady-state sequence showing the cisternal segment of the left hypoglossal nerve with an abnormally tortuous course dashed arrows). Arrowhead: Medial edge of the left hypoglossal canal.

DISCUSSION

Given the clinical findings of the present patient, a fall during mountain hiking may have caused left HN palsy due to OC fractures. The patient initially demonstrated tongue atrophy on the left side with deviated protrusion. However, the function of the right HN deteriorated for 1 month after coil embolization, resulting in bilateral HN palsy. CT performed immediately after the fall revealed right OC fractures. In addition, CT at the onset of the subarachnoid hemorrhage revealed dominant perimedullary clots on the right side. Furthermore, post-embolization CT indicated that the PICA aneurysm was located at the level of the hypoglossal canal. Therefore, we speculated that the right HN may have been damaged initially by OC fractures, followed by subarachnoid hemorrhage due to rupture of PICA aneurysm, which led to delayed palsy.

Based on the clinical findings, the PICA aneurysm developed and ruptured within 3 days following the fall. Previous reports documented variable lengths of time between injury and rupture of a traumatic cerebral aneurysm.[ 8 , 9 ] Therefore, careful observation for a prolonged period is recommended for patients with trauma involving the craniocervical region, especially those with OC fractures. In the present case, a traumatic aneurysm was successfully treated using stent-assisted coil embolization. With the remarkable evolution of embolic materials and accumulation of cases, endovascular therapy may be a safe treatment option for traumatic PICA aneurysms.

Injuries involving the head-and-neck regions are common among mountain hikers.[ 2 ]

Furthermore, victims of falls are more likely to occur in older mountain hikers due to frequent vision impairments.[ 5 ] OC fractures may not be diagnosed with routine clinical and radiological examinations.[ 3 ] Anatomically, the OCs exhibit morphological variability.[ 1 ] In addition, OC fractures can occur even with minor head trauma.[ 6 ] Careful evaluation using clinical and radiological examinations is essential for an accurate diagnosis and appropriate treatment. Repeated and thorough evaluations are especially important for trauma in mountain hikers, particularly among older individuals.

CONCLUSION

Traumatic PICA aneurysms may be complicated by HN palsy. A thorough evaluation using both clinical and radiological examinations is essential for accurate diagnosis and appropriate treatment.

Ethical approval

The Institutional Review Board has waived the ethical approval for this study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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