Brain motion in patients with skull defects: B-mode ultrasound observations on respiration-induced movements
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Since ancient times, brain motion has captured the attention of human beings. However, there are no reports about morphological changes that occur below the cortex or skin flap when a patient, with an open skull breathes, coughs, or engages effort. Thus, the aim of this study was to characterize brain motion caused by breathing movements in adults with an open skull.
Twenty-five craniectomized patients were studied using B-mode ultrasonography during early and late postoperative periods. Twelve patients were analysed during surgery. Brain movements induced by breathing activity were assessed in this prospective observational study.
Taking as a reference the cranial base, an increase in intrathoracic pressure was accompanied by a rise of the brain due to the expansion of the basal cisterns. Greater increases in intrathoracic pressure (resulting from the Valsalva manoeuvre and coughing) propelled the brain in a block from the foramen magnum towards the craniectomy, mainly in structures near the tentorial incisure. Prolonging the Valsalva manoeuvre also resulted in thickening of the cortical mantle attributable to vascular congestion. The magnitude of these movements was directly related to breathing effort.
The increase in intrathoracic pressure was immediately transmitted to the brain by the rise of cerebrospinal fluid, while brain swelling attributable to vascular congestion showed a brief delay. The Valsalva manoeuvre and coughing caused abrupt morphological changes in the tentorial hiatus neighbouring structures because of the distension of the basal cisterns. These movements could play a role in the pathophysiology of the syndrome of trephined.
KeywordsBrain motion Craniectomy (B-mode) ultrasound Valsalva manoeuvre Cough Syndrome of trephined
The authors wish to thank Silvana A. Sanguinetti, M.D. for translating the original article into English.
Conflict of interest
The authors declare that they have no conflict of interest.
Ambulatory patient No. 13. Parasagittal view. The transducer was placed on the top of the head. The thalamus is found in the centre of the image, and the brainstem can be seen toward hour 6. The skull base is seen as a hyperechoic rim at the bottom of the image. Hyperpnea. The descent of the brainstem during inspiration and its ascent during exhalation is shown. (MPG 6194 kb)
Ambulatory patient No. 19. Coronal view. Coughing. Abrupt movements can be seen at the brainstem and diencephalic levels. Towards hour 4, the fourth ventricle (hypoechoic) with its choroid plexus (hyperechoic) and the occipital foramen can be seen. The morphological changes seem to be due to parenchymal propulsion caused by CSF. No changes can be seen in the distance between the cortical surface and the ependyma of the supratentorial ventricular cavities, which could be attributed to vascular congestion. (MPG 2970 kb)
Ambulatory patient No 10. Coronal view. Valsalva manoeuvre. See Fig. 1 for descriptive text. (MPG 4682 kb)
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