Unruptured intracranial aneurysms: relation between morphology and wall strength.

AIM OF THE STUDY: To determine the morphological features distinguishing small unruptured saccular intracranial aneurysms (sIAs) with high and low wall strength (WS) in post mortem subjects. CLINICAL RATIONALE FOR THE STUDY: Subarachnoid haemorrhage caused by sIA rupture is associated with increased mortality and morbidity. Analysis of the morphology and biomechanical properties of sIAs might facilitate the identification of clinically relevant risk factors for sIA rupture. MATERIAL AND METHODS: Eight single unruptured sIAs were found among eight subjects during 184 post mortem examinations. After assessment of the dimensions, aspect ratio (AR), size ratio (SR), height/width ratio (HW), bottleneck factor (BNF), and shape, sIAs with adjacent cerebral arteries were subjected to quasi-static increasing pressure until the wall of the cerebral artery or sIA ruptured. RESULTS: In three specimens, the sIA ruptured at a significantly lower average pressure than the other cases, in which the rupture occurred within the wall of the adjacent cerebral artery (769 vs. 1,259 mmHg; p = 0.035). The sIAs with low WS, i.e. sIAs that ruptured during experiments, were characterised by significantly increased dome dimensions compared to sIAs with high WS (p < 0.05). At the same time, no significant differences were observed between high and low WS categories regarding AR, SR, HW, and BNF, or the presence of an irregular dome shape. CONCLUSIONS AND CLINICAL IMPLICATIONS: Dome dimension was the only feature that distinguished unruptured sIAs as having low or high WS, and this supports observations that sIAs with increased dome dimensions are characterised by an increased risk of rupture. Thus, dome dimension may be more useful than other morphometric parameters, such as AR, SR, HW and BNF, in assessing the rupture risk assessment of small unruptured sIAs.

Rupture pressure values of cerebral arteries in the presence of unruptured intracranial aneurysm.

Cerebral arteries (CAs) are prone to the saccular aneurysm formation. Since aneurysms may be considered as balloon-like dilations of the locally weakened arterial wall, it should be determined whether the presence of intracranial aneurysm is related to the generalized weakening of CAs. Among 184 consecutive forensic autopsies, eight brains with a single unruptured saccular aneurysm were identified. Aneurysms with adjacent CAs and specific CA segments were excised, namely: the anterior communicating artery complex, and bifurcations of the basilar artery, internal carotid arteries, and middle cerebral arteries. Then, aneurysm and CA specimens were subjected to pressure-inflation tests until rupture occurred at the arterial bifurcation or at the wall of the CA or aneurysm. The same protocol was applied to the control group composed of CAs excised from eight brains without aneurysm. No significant differences were noted between the experimental and control groups, depending on the mean rupture pressure (1054 vs. 1048 mmHg) and rupture site (bifurcation vs. wall) of the analyzed specimens. These findings indicate that the presence of unruptured saccular aneurysm is not related to generalized weakening of CAs among autopsy subjects. Moreover, the CA bifurcations do not represent regions of decreased wall strength.

Impact of inflammation-related degenerative changes on the wall strength of unruptured intracranial aneurysms: a pilot study.

INTRODUCTION: Saccular intracranial aneurysm (sIA) rupture is a serious cerebrovascular event associated with inflammatory destructive processes leading to gradual weakening of the sIA wall. The aim of the present study was to identify the morphological and histological determinants for low wall strength in unruptured sIAs harvested from autopsy subjects. MATERIAL AND METHODS: A total of eight single unruptured sIAs were identified and excised with adjacent cerebral arteries during 8 of 184 postmortem examinations. The dome morphology was assessed for each sIA at a constant pressure of 100 mmHg. Then, after 5 preconditioning cycles which assured muscle fibre relaxation, sIA specimens were subjected to gradually increasing intraluminal pressure at a rate of 20 mmHg/s until rupture of the sIA or cerebral artery was achieved. Micro-structural degenerative changes and inflammatory cell infiltration within the sIA wall were quantitatively analysed after pressurization of the sIA specimens. The microscopic analysis of the slides stained with histological methods (HE, Mallory trichrome, Masson trichrome, orcein) and immunohistochemical methods (LCA, CD3, CD68) was performed. RESULTS: The wall of the sIA ruptured in three specimens, while in the other cases, rupture occurred at the arterial wall. The mean maximal dome size was significantly larger in sIAs with low wall strength, that is, in sIAs that ruptured during pressurization, than in sIAs with high wall strength (6.46 mm vs. 2.43 mm, p = 0.034). Moreover, a significantly higher average percentage of wall hyalinization in sIAs that ruptured than in sIAs that did not rupture was observed (30% vs. 0%, p = 0.006). In contrast, the degree of inflammatory cell infiltration did not differ between the wall strength categories. CONCLUSIONS: Our results support the observations that larger sIAs may be at a higher risk of rupture. Histological analysis revealed that hyalinization corresponds to the weakened regions of the wall of unruptured sIAs.

Isolated condylar fractures diagnosed by post mortem computed tomography.

Due to their anatomical location, occipital condylar fractures (OCFs) are usually not observed during traditional autopsies and are therefore considered a rare injury. The aim of this study was to determine the true frequency of OCFs using post-mortem computed tomography (PMCT) in traumatic casualties. We retrospectively analyzed 438 PMCT studies of victims of traffic accidents, falls from height, violence, and low-energy head injuries (324 males and 114 females). OCFs were present in 22.6% of cases (n = 99), mostly in victims of railway accidents (48.5%, n = 17), falls from height (26.6%, n = 29), cyclists (24%, n = 6), and pedestrians hit by cars (22.5%, n = 29). Isolated OCFs were found in 5.5% of cases (n = 24), most often in cyclists (12%, n = 3) and pedestrians (9.3%, n = 12) hit by cars. There were no OCFs in the cases of fatalities caused by violence or accidental low-energy head injury. PMCT scans revealed that OCFs are common in high-energy injury fatalities and can be useful for determining the mechanism of trauma more precisely.

Symptomatic medulla compression by vertebral artery.

OBJECTIVE: Vertebral artery medulla compression syndrome (VAMCS) is a very rare condition manifesting as different neurological focal deficits. The case of a 36-year-old male with symptomatic brainstem compression by vertebral artery (VA) treated by means of microvascular decompression (MVD) and a review of the literature is presented. CASE REPORT: On admission, a 36-year-old patient presented with hypoalgesia, hypothermesthesia and hemiparesis on the left side. Magnetic resonance imaging (MRI) of the head disclosed the right VA loop compressing the ventrolateral medulla and excluded other entities such as brain tumor, stroke and multiple sclerosis. Since displacement and significant compression of the right pyramidal tract was confirmed by diffusion tensor imaging (DTI), neurovascular compression syndrome was diagnosed. The patient underwent MVD of the medulla using a Gore-Tex implant as a separating material via the right far-lateral approach. The left hemiparesis and hemisensory loss remitted rapidly after the procedure. The post-procedural neurological improvement was maintained at one year follow-up. Based on a review of the literature, a total of 33 cases of surgically treated VAMCS has been reported so far. CONCLUSION: VAMCS should be considered as the cause of neurological deficits when other pathological entities are ruled out. In symptomatic conflict of the VA with the medulla, microvascular decompression using a Gore-Tex implant can be an effective method of treatment. Nevertheless, a statistical analysis on all reported cases showed favorable results using the VA repositioning technique when compared with MVD (success rate 91% vs. 58%, p<0.05).

Age dependence of critical pressure in the segments and branches of the circle of Willis.

Spontaneous intracranial haemorrhage is one of the most dramatic neurological disasters. The source of haemorrhage is linked to the pathology of the arterial wall or is unknown. Because the risk of haemorrhagic stroke increases with age, we tried to investigate the relationship between age and rupture pressure of cerebral arteries. In the presented study, 51 segments of large cerebral arteries (at the level of the circle of Willis and its incoming and outgoing branches) were obtained from 33 cadaver brains aged 12-86 years. The segments were pressurized up to the rupture. The rupture pressure was noted. The highest observed pressure was 4.3atm in specimen aged 24 years. The lowest pressure 1.19atm was observed in specimen aged 80 years. The mean value of rupture pressure of all investigated segments was 2.28atm. Statistical analysis showed a nonlinear exponential decrease of the rupture pressure of the large cerebral arteries with age. The main conclusion from our study is that drop of cerebral arteries strength is observed to the age of 40. Later this lowering is visible but not so evident.

Experimental determination of rupture pressure and stress of adventitia of human middle cerebral arteries.

Background Intracranial arterial dissections might be attributed to the particular biomechanical properties of their specific layers. Also, knowledge of adventitia properties would be crucial in the context of intracranial balloon angioplasty. Aims The purpose of this work was to determine the rupture pressure of separated adventitia and compare it to intact cerebral arterial segments. Methods Brain specimens were harvested from 14 autopsy subjects (age range from 23 to 86 years). Pressure-inflation tests were conducted on proximal segments of middle cerebral arteries and separated adventitia layers from contralateral arteries to assess the rupture pressure values. Results The averaged rupture pressure of adventitia layers was 1.41 SD 0.25 atm (1072 SD 190 mmHg), whereas for intact arterial segments it was 2.32 SD 0.70 atm (1763 SD 532 mmHg) and diminished with age according to nonlinear regression trends. The difference beetween the aformentioned rupture pressures was positively correlated with rupture pressure of intact arterial segments ( R2 = 0.88; p < 0.001). Conclusions The obtained experimental results indicate a leading role of adventitia in building arterial strength under supraphysiological pressure conditions. The greater the rupture pressure of complete cerebral arteries, the smaller the contribution of adventitia in overall wall resistance.