'Bony' Stroke: Bone Defects Can Cause
Recurrent Stroke

April 20, 2023

An unusual cause of ischemic stroke — the presence of structural bone and cartilage anomalies which cause mechanical stress to arteries supplying the brain — has been highlighted in a new case series.

These so-called "bony strokes" constitute a possible cause of recurrent ischemia in the same vascular territory as previous episodes, note the authors, led by Johanna Haertl, MD, Technical University of Munich, School of Medicine, Munich, Germany.

"In patients with recurrent strokes in one vascular territory the presence of a symptomatic anatomic bone or cartilage anomaly may be considered as a differential diagnosis after sufficient exclusion of competing etiologies of an ischemic stroke," they conclude.

"Due to the possibly high risk of stroke recurrence and potentially causative treatment options, bony strokes seem to be highly relevant for clinical practice,” they add.

The study was published online April 13 in the journal Stroke.

In their report, investigators explain that diagnosis of a bony stroke is based on a combination of imaging devices including CT, MRI, angiography, and sonography of brain supplying vessels.

In addition to conventional static imaging, dynamic imaging modalities with the patients' head in a fixed rotation or reclination has been shown to be useful as this enables the detection of a compressive effect on brain supplying arteries caused by head movement.

They note that these bony strokes have been described previously — mainly as single case reports or small case series — but a systematic evaluation of each anatomical type of bony stroke is currently lacking.

For the current paper, the authors describe the identification and therapeutic workup of six patients with a bony stroke among 4200 patients with ischemic stroke treated from January 2017 to March 2022 at their comprehensive stroke care center, constituting an incidence of 0.14%.

But they caution, "Given our retrospective study design, the method of patient acquisition, and the lack of systematic evaluation of bony strokes during acute stroke treatment, epidemiologic conclusions can be drawn only very carefully."

In each of these six cases, the recurrent stroke was found to be caused by large artery embolism from mechanical stress by bone or cartilage anomalies on arteries supplying the brain.

"Our case series aims to raise awareness for the rare entity of bony strokes, emphasizing the necessity to evaluate structural bone or cartilage lesions as a possible cause of ischemic stroke in patients with stroke recurrence of unknown cause in one vascular territory. We further aim on highlighting individual diagnostic and therapeutic options," they state.

They note that it has previously been suggested that ischemic strokes based on bone or cartilage anomalies are more common in the relatively young patients with stroke, which is in line to their current patient data (mean age, 55 years), but this may reflect a selection bias.

A medical history with an association between changes in the head position and the occurrence of ischemic stroke may also raise awareness of the possibility of a bony stroke.

The authors outline treatment options for bony stroke, which they describe as diverse and include conservative treatment, endovascular stenting, occlusion of the affected vessel, surgical bypass, and bone/cartilage removal.

From a pathophysiologic point of view, it seems reasonable to eliminate a causative lesion by surgical removal of the mechanical stressor, they note.

In cases of vascular stenting, they caution that the remainder of the mechanical stressor may provoke stent fracture and recurrent stroke, which occurred in two of their patients, a situation that may be observed more often in the future with the increasing use of vascular stenting.

The authors report that, compared with annual stroke rates in atrial fibrillation patients, stroke recurrence in this patient cohort ahead of definite treatment was high (cumulative 2.14 strokes per year). And as no patient had further ischemia after treatment, they argue that diagnosis and appropriate treatment of bony stroke may reduce or even eliminate the risk for future stroke recurrence.

They propose that for the diagnosis, an exact medical history, with emphasis on a possible change of head position on the onset of stroke symptoms, is useful.  

Furthermore, previously acquired diagnostic scans including CT or MRI may be evaluated for a symptomatic vessel-bone or cartilage contact. Then, the additional application of dynamic imaging modalities, including dynamic ultrasound of brain supplying vessels and CT-angiography, may be discussed.

"An appropriate diagnosis and the evaluation of individual and interdisciplinary treatment options seem crucial to prevent recurrent ischemic strokes. Future prospective trials seem mandatory to optimize patient care," they conclude.

The study had no specific funding. Co-author Jan S. Kirschke, MD, received research support from the German Research Foundation, Bonescreen, H2020 European Research Council, and Philips. The other authors report no relevant financial relationships.

Stroke. Published online April 13, 2023. Abstract 

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