Magnetic resonance imaging assessment of brainstem distortion associated with a supratentorial mass

Brain Herniation and Intracranial Hypertension

This article introduces the basic concepts of intracranial physiology and pressure dynamics. It also includes discussion of signs and symptoms and examination and radiographic findings of patients with acute cerebral herniation as a result of increased as well as decreased intracranial pressure. Current best practices regarding medical and surgical treatments and approaches to management of intracranial hypertension as well as future directions are reviewed. Lastly, there is discussion of some of the implications of critical medical illness (sepsis, liver failure, and renal failure) and treatments thereof on causation or worsening of cerebral edema, intracranial hypertension, and cerebral herniation.

Brainstem injury associated with supratentorial lesions is revealed by electronystagmography of the cold caloric reflex test

To explore the brainstem injury associated with supratentorial lesions, we conducted analysis of ICP levels and detected ENG parameters by using the cold caloric reflex test and histopathological examinations of the brainstem. Rat model of intracerebral hemorrhage was well-established in the study of supratentorial lesions of varying severities (n=210). Intracerebral pressure monitoring and electronystagmography of the cold caloric reflex test were simultaneously performed in animals. Apoptotic, immunohistochemical, and histopathological changes in different segments of the brainstem were investigated at various time intervals. Electronystagmography parameters were analyzed by cold caloric reflex test. The result showed that the increase of intracerebral pressure was correlated with lesion severity including elevating levels and rostral-caudal progression of neuronal apoptosis, demyelination, N-methyl-D-aspartate cell receptor down-regulation (r=0.815), and histopathological changes. Mutiple discrimination analysis of electronystagmography parameters presented a diagnostic accuracy rate of 79.5% in localizing brainstem injury. In conclusion, our data demonstrated that electronystagmography monitoring along with the cold caloric reflex test performed a favorable effect on the estimation of brainstem injury in ICH rat model, which provided a potential bedside diagnostic tool to assess and predict the progress of supratentorial lesion patient in future.

Radiographic assessment of cranial gunshot wounds

Though advances in MRI will undoubtedly increase its use, particularly in the subacute period, CT will likely continue its primary role in the management of these injuries in the foreseeable future. The spectrum of imaging features of cranial gunshot injuries is vast, because they encompass all of the findings encountered in closed head injury in addition to the wide variety of problems associated with penetration. Thus, only a brief summary of the many varied aspects of this complex problem is presented here as a review of the more salient issues.

Differential regional brain growth and rotation of the prenatal human tentorium cerebelli

Folds of dura mater, the falx cerebri and tentorium cerebelli, traverse the vertebrate endocranial cavity and compartmentalize the brain. Previous studies suggest that the tentorial fold has adopted an increasingly important role in supporting the increased load of the cerebrum during human evolution, brought about by encephalization and an adaptation to bipedal posture. Ontogenetic studies of the fetal tentorium suggest that its midline profile rotates inferoposteriorly towards the foramen magnum in response to disproportionate growth of the cerebrum. This study tests the hypothesis that differential growth of the cerebral and cerebellar components of the brain underlies the inferoposterior rotation of the tentorium cerebelli during human fetal development. Brain volumes and tentorial angles were taken from high-resolution magnetic resonance images of 46 human fetuses ranging from 10 to 29 gestational weeks. Apart from the expected increases of both supratentorial and infratentorial brain volumes with age, the results confirm previous studies showing a significant relative enlargement of the supratentorial volume. Correlated with this enlargement was a rotation of the midline section of the tentorium towards the posterior cranial base. These findings support the concept that increases of supratentorial volume relative to infratentorial volume affect an inferoposterior rotation of the human fetal tentorium cerebelli. These results are discussed in the context of the role played by the tentorium cerebelli during human evolution and underline implications for phylogenetic and ontogenetic models of encephalization.

Relation between brain displacement and local cerebral blood flow in patients with chronic subdural haematoma

OBJECTIVES

To evaluate the relation between brain displacement, clinical signs and symptoms, and local cerebral blood flow (lCBF) in patients with chronic subdural haematoma (CSDH).

METHODS

Forty five patients (age range 58-87 years, mean 71.9 (SD 8.4)) with unilateral CSDH were studied. Patients were categorised into three groups: I, headache (n=16); II, paresis (n=14); and III, mental change (n=15). T1 weighted MR images were obtained in all patients preoperatively. Quantitative values of maximum haematoma thickness, midline shift, and brain rotation angle were measured on axial and coronal MR images. In 21 patients, lCBF was measured by Xe enhanced CT. Values for lCBF were obtained in selected regions of interest in the frontal cortex, thalamus, and hemisphere on both the haematoma and contralateral sides.

RESULTS

The lCBF reduction in the ipsilateral frontal cortex showed the best linear correlation with haematoma thickness (r=0.57), whereas the reduction in the ipsilateral thalamus had the most significant correlation with pineal shift (r=0.65) and third ventricle incline (r=0.67). In patients with paresis, lCBF decreased significantly on the ipsilateral side of both the frontal cortex and thalamus (p<0.05), whereas patients with mental change showed a significant reduction of lCBF on both sides of the thalamus (p<0.01) and in the ipsilateral frontal cortex (p<0.01).

CONCLUSIONS

The lCBF reduction and clinical symptoms correlated well with local brain displacement in patients with CSDH. The lCBF in the central cerebral area including the thalamus was reduced in patients with clinical signs. The mental changes found were thought to derive from mild impairment of consciousness due to upper brain stem displacement.

Dynamics of cerebral blood flow and metabolism in patients with cranioplasty as evaluated by 133Xe CT and 31P magnetic resonance spectroscopy

OBJECTIVE

Prolonged improvement in neurological and mental disorders has been seen after only cranioplasty in patients initially treated with external decompression for high intracranial pressure. The objective was to evaluate, using 133Xe CT and 31P magnetic resonance spectroscopy (MRS), how restoring the bone itself can influence cerebral blood flow and cerebral energy metabolism after high intracranial pressure is attenuated.

METHODS

Seven patients (45-65 years old) who had undergone external decompression to prevent uncontrollable intracranial hypertension after acute subarachnoid haemorrhage were evaluated. Cerebral blood flow and metabolic changes were evaluated before and after cranioplasty.

RESULTS

The ratio of phosphocreatine to inorganic phosphate (PCr/Pi), which is a sensitive index of cerebral energy depletion, was calculated and beta-ATP was measured. The cerebral blood flow value in the thalamus was normalised, from 44 (SD 9) to 56 (SD 8) ml/100 g/min (P < 0.01) and the value in the hemisphere increased from 26 (SD 3) to 29 (SD 4) ml/100 g/min on the side with the bone defect. The PCr/Pi ratio improved greatly from 2.53 (SD 0.45) to 3.01 (SD 0.24) (P < 0.01). On the normal side, the values of cerebral blood flow and PCr/Pi increased significantly (P < 0.01) after cranioplasty, possibly due to transneural suppression. The pH of brain tissue was unchanged bilaterally after cranioplasty.

CONCLUSION

Cranioplasty should be carried out as soon as oedema has disappeared, because a bone defect itself may decrease cerebral blood flow and disturb energy metabolism.