The Monro-Kellie doctrine in its own context.

In 1783, Alexander Monro secundus maintained that because the brain is enclosed in a case of bone and its substance is nearly incompressible, the quantity of blood within the head must be the same, or very nearly the same, at all times. Years later, this hypothesis was experimentally supported by George Kellie, and became known as the Monro-Kellie doctrine. However, this doctrine encountered resistance. Its reviewers have agreed to point out the historically understandable error of not having considered the CSF as a normal intracranial volume. Yet, almost nothing has been published about some of the physiological, pathophysiological, and therapeutic ideas prevailing at that time that may have influenced Monro's hypothesis. Lastly, and perhaps most importantly, it is not clear why Monro, who knew the ventricular system in detail, did not include it as a potential compensatory compartment for changes in the intracranial blood volume.

Manuel Balado y las diferenciasde presión craneal y espinal / Manuel Balado and the cranial and spinal pressure differences

Manuel Balado (1897-1942), pionero de la neurocirugía argentina, es más conocido por sus estudios sobre la vía óptica y la sistematización de la iodoventriculografía. Sus inquietudes, sin embargo, abarcaron numerosos otros campos, siendo uno de ellos la existencia de diferencias de presión entre compartimientos craneales y espinales. En sus Lecciones de Cirugía Neurológica, el primer texto exclusivo de la especialidad en la Argentina, hizo una descripción original de los mismos. Reproducimos aquí varios de los mismos, la mayoría aún válidos, y los analizamos en su contexto y a la luz de los conocimientos actuales. No hemos hallado descripciones similares en la bibliografía de su tiempo(AU)

Manuel Balado (1897-1942), a pioneer of Argentinian neurosurgery, is best known for his studies on the optic pathway and iodoventriculography. Their concerns, however, encompassed numerous other fields, one of them being the pressure differences between the cranial and spinal compartments. In his Lessons on Neurological Surgery, the first exclusive text of the specialty in Argentina, he made an original description of them. We reproduce here several of his schemes, most of them still valid, and we analyze them in their context and in the light of current knowledge. We did not find similar descriptions in the bibliography of his time(AU)

Punción ventricular transorbitaria: Revisión de la técnica y reporte de un caso / Transorbital Ventricular Puncture: Review of the technique and report of a case

La punción ventricular transorbitaria (PTO) es una técnica rápida y sencilla aunque poco utilizada en la actualidad. Como puede realizarse en la cama del paciente, resulta ideal en aquellos con hidrocefalia aguda rápidamente evolutiva o con enclavamiento transtentorial inminente o reciente, en quienes el acceso expeditivo a las cavidades ventriculares puede salvarles la vida. Revisamos aquí el desarrollo histórico de la técnica desde su descripción original en 1933. Por último, presentamos el caso de una paciente con hidrocefalia aguda secundaria a edema cerebeloso, en quien el empleo de la PTO dio tiempo para implementar el tratamiento definitivo. La técnica utilizada por nosotros consistió en un ingreso transpalpebral, por detrás del reborde orbitario superior y a nivel mediopupilar, con una trayectoria dirigida hacia la sutura sagital, dos a tres traveses de dedo por detrás de la sutura coronal(AU)

Transorbital ventricular puncture (TOP) is a fast and simple but poorly understood technique. As it can be performed at the patient's bedside, it is ideal in patients with rapidly evolving acute hydrocephalus or with imminent or recent transtentorial herniation, in whom expeditious access to the ventricular cavities can be life-saving. We review the historical development of the technique since its original description in 1933. Finally we present the case of a patient with acute hydrocephalus secondary to cerebellar edema, in whom the use of TOP allowed time to implement definitive treatments. The technique used by us consisted of an entry point through the upper eyelid, behind the superior orbital rim, and at the midpupillary line, with a trajectory aimed towards the sagittal suture two to three finger widths behind the coronal suture(AU)

Brain motion and volume transmission: Keeping the interstice flowing.

Human brain undergoes two different kinds of movements: subtle pulsatile ones associated with the cardiac cycle and others of a greater magnitude related to breathing activity. These motions constitute a pumping force for the circulation of cerebrospinal fluid (CSF). Moreover, brain motion (BM) plays a fundamental role as a driving force for the interstitial and CSF flow of tracers. We hypothesize that BM is more than a mere consequence of cardiac and respiratory activities; that it would be part of a fundamental physiological mechanism by propelling the interstitial flow of messengers, a mechanism also known as 'non-synaptic transmission' or 'volume transmission' (VT). Intracranial hypertension (ICH), a frequent complication of severe head trauma, is related to brain stiffness. Under this circumstance, not only brain perfusion could be at risk, but BM could be engaged as well. Decompressive craniectomy, presently indicated to reduce ICH refractory to medical treatment, could play a role in helping BM and VT. Once brain swelling is overcome, the closure of the cranial bone defect would ensure the recovery of the spatial and temporal patterns of BM. We discuss evidence supportive of the necessary role of a minimal and sequential BM for an adequate VT.

Brain motion in patients with skull defects: B-mode ultrasound observations on respiration-induced movements.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Maniobra de valsalva y tos en pacientes craniectomizados: observaciones ecográficas (modo B) en favor de la craneoplastia precoz / Valsalva manouver & cought in craniectomized patients: ultrasound observations (B mode) favouring early craneoplasty

Objetivo: evaluar los movimientos del parénquima encefálico durante la maniobra de Valsalva y la tos en pacientes craniectomizados y discutir sus implicancias fisiopatológicas y terapéuticas. Material y método. Catorce pacientes adultos con craniectomías mayores de 30 cm2 y colgajos pulsátiles fueron estudiados ecográficamente. La atención se focalizó en los cambios morfológicos intracraneanos inducidos por la maniobra de Valsalva y la tos.Resultados: durante la maniobra de Valsalva y la tos el cerebro fue propulsado en bloque hacia la craniectomía. Movimientos notorios se observaron a nivel centroencefálico y este fenómeno se atribuyó fundamentalmente al ascenso de LCR desde la columna y la distensión de las cisternas de la base. La magnitud de los cambios morfológicos fue proporcional al esfuerzo respiratorio y la presión intracraneana. Conclusiones: la maniobra de Valsalva y la tos provocaron cambios morfológicos bruscos e importantes a nivel centroencefálico, A la luz de teorías recientes se discuten las eventuales consecuencias de esta movilidad patológica sobre las estructuras témporomesiales y las funciones cognitivas. Estas observaciones constituyen un firme argumento en favor de la craneoplastia precoz.