Comparison of direct measurement of intracranial pressures and presumptive clinical and magnetic resonance imaging indicators of intracranial hypertension in dogs with brain tumors

BACKGROUND

Intracranial hypertension (ICH) is often presumptively diagnosed based on clinical or imaging findings. Clinical or imaging surrogates of ICH are not usually validated with reference standard direct intracranial pressure (dICP) recordings.

HYPOTHESES

Dogs with brain magnetic resonance imaging (MRI) or clinical features of presumed ICH would have higher dICP than dogs lacking those features.

ANIMALS

Twenty dogs with gliomas and 3 normal controls.

METHODS

Prospective, convenience study. Dogs were presumptively categorized with normal ICP or ICH from scores generated from described clinical and brain MRI indicators of ICH. dICP was recorded in anesthetized dogs using an intraparenchymal microsensor and compared between groups.

RESULTS

dICP was not different between control (10.4 ± 2.1 mm Hg) and dogs with glioma (15.6 ± 8.3 mm Hg), or between dogs in clinically predicted ICP groups. Compared with dogs with MRI-predicted normal ICP, MRI-predicted ICH dogs had higher dICP (10.3 ± 4.1 versus 19.2 ± 7.9 mm Hg, P = .004), larger tumors (1.45 ± 1.2 versus 5.71 ± 3.03 cm3 , P = .0004), larger optic nerve sheath diameters, and 14/14 (100%) displayed structural anatomical shifts on MRI. At a dICP threshold of 15 mm Hg, the sensitivity of MRI for predicting ICH was 90% and the specificity 69%.

CONCLUSIONS AND CLINICAL RELEVANCE

dICP measurements are feasible in dogs with brain tumors. MRI features including brain herniations, mass effect, and optic nerve size aid in the identification of dogs with ICH. Clinical estimation of ICP did not discriminate between dogs with and without ICH.

Transcranial Doppler Ultrasound Examination in Dogs with Suspected Intracranial Hypertension Caused by Neurologic Diseases

Background

Transcranial Doppler ultrasound examination (TCD) is a rapid, noninvasive technique used to evaluate cerebral blood flow and is useful for the detection of intracranial hypertension in humans. However, the clinical usefulness of TCD in diagnosing intracranial hypertension has not been demonstrated for intracranial diseases in dogs.

Objectives

To determine the association between the TCD variables and intracranial hypertension in dogs with intracranial diseases.

Animals

Fifty client‐owned dogs with neurologic signs.

Methods

Cross‐sectional study. All dogs underwent TCD of the basilar artery under isoflurane anesthesia after magnetic resonance imaging (MRI). Dogs were classified into 3 groups based on MRI findings: no structural diseases (group I), structural disease without MRI evidence of intracranial hypertension (group II), and structural disease with MRI evidence of intracranial hypertension (group III). The TCD vascular resistance variables (resistive index [RI], pulsatility index [PI], and the ratio of systolic to diastolic mean velocity [Sm/Dm]) were measured.

Results

Fifteen, 22, and 13 dogs were classified into groups I, II, and III, respectively. Dogs in group III had significantly higher Sm/Dm (median, 1.78; range, 1.44–2.58) than those in group I (median, 1.63; range, 1.43–1.75) and group II (median, 1.62; range, 1.27–2.10). No significant differences in RI and PI were identified among groups.

Conclusions and Clinical Importance

Our findings suggest that increased Sm/Dm is associated with MRI findings of suspected intracranial hypertension in dogs with intracranial diseases and that TCD could be a useful tool to help to diagnose intracranial hypertension.

Changes in Intracranial Morphology, Regional Cerebral Water Content and Vital Physiological Variables during Epidural Bleeding

Epidural bleeding was produced in 8 anaesthetised and heparinised dogs by an artificial system. Changes in vital physiological variables were related to intracranial shifts and tissue water content assessed with MR imaging. Six animals survived while 2 succumbed. In the surviving animals intracranial shifts and compressions remained unchanged from an early stage. The cerebral perfusion pressure was reduced from between 80 and 110 mm Hg to between 40 and 60 mm Hg. Some increase in supratentorial white matter tissue water was observed. In the lethal experiments cerebral perfusion pressure fell to less than 40 mm Hg. Moreover, secondary delayed anatomical changes were seen including hydrocephalus. Increase in cerebral tissue water was more intense and widespread than in the survivors. These findings indicate that the outcome of epidural bleeding is related to cerebral perfusion pressure with secondary deterioration resulting from additional volume loading from increased tissue water and hydrocephalus.

Imaging of head trauma

Imaging is an indispensable part of the initial assessment and subsequent management of patients with head trauma. Initially, it is important for diagnosing the extent of injury and the prompt recognition of treatable injuries to reduce mortality. Subsequently, imaging is useful in following the sequelae of trauma. In this chapter, we review indications for neuroimaging and typical computed tomography (CT) and magnetic resonance imaging (MRI) protocols used in the evaluation of a patient with head trauma. We review the role of CT), the imaging modality of choice in the acute setting, and the role of MRI in the evaluation of patients with head trauma. We describe an organized and consistent approach to the interpretation of imaging of these patients. Important topics in head trauma, including fundamental concepts related to skull fractures, intracranial hemorrhage, parenchymal injury, penetrating trauma, cerebrovascular injuries, and secondary effects of trauma, are reviewed. The chapter concludes with advanced neuroimaging techniques for the evaluation of traumatic brain injury, including use of diffusion tensor imaging (DTI), functional MRI (fMRI), and MR spectroscopy (MRS), techniques which are still under development.

Cerebrospinal fluid drainage and cranial decompression prolong survival in rats with fulminant hepatic failure

Fulminant hepatic failure (FHF) is a devastating disease. Liver transplantation is the definitive treatment. However, a third of these patients die due to brain edema before a donor becomes available. Cerebrospinal fluid (CSF) drainage and decompressive craniectomy have been used to treat brain edema in brain trauma and hemispheric stroke. However, their role in brain edema associated with FHF has not been examined. In this study we evaluated the potential effects of CSF drainage and decompressive craniectomy on survival in FHF using an experimental model in rats. In CSF drainage experiments all animals had ventriculostomy placed. Five days later FHF was induced with d-galactosamine. Those FHF rats that progressed into comatose stages either received CSF aspiration or did not. In separate experiments the study rats had either a decompressive craniectomy or a sham procedure. FHF was induced 5 days later. We found that both CSF drainage and decompressive craniectomy significantly increased survival of FHF rats compared with the controls: 53.2 +/- 1.1 vs. 48.7 +/- 1.5 h (P = 0.031), and 69.4 +/- 3.9 vs. 53.7 +/- 3.2 h (P = 0.009), respectively. In conclusion, these findings suggest that CSF drainage and decompressive craniectomy may increase the window of opportunity for liver transplantation.

Hydrocephalus: obliterated perimesencephalic cisterns and the danger of sudden death

OBJECTIVE

We reported a possible risk factor which could identify patients with chronic hydrocephalus who are risk for sudden death.

METHODS

A retrospective review of medical records and computed tomographic (CT) scans was conducted on three patients with chronic hydrocephalus who suffered acute cardiorespiratory arrest without those signs which are normally associated with a progressive worsening of hydrocephalus.

RESULTS

All three of these patients were awake and communicative shortly before the life threatening or terminal event. All had experienced some recent worsening of neurologic signs or symptoms, but none had shown a progressive impairment of consciousness or major neurologic decline ordinarily associated with life threatening elevation of intracranial pressure. Absence of the perimesencephalic cisterns on head CT scans done prior to or just after the life threatening event was the only new radiologic finding common to all these patients.

CONCLUSIONS

The absence of the perimesencephalic cisterns in an awake and alert patient with severe hydrocephalus indicates that the patient may be at risk for neurogenic cardiorespiratory failure. In such cases, (especially when there has been a recent, albeit mild, change in neurologic signs or symptoms), the neurologist should urge emergency ventriculostomy or shunting for the hydrocephalus.

The history of Swedish neuroradiology

The history of Swedish neuroradiology is reviewed.