Clinical and Diagnostic Imaging Features of Brain Herniation in Dogs and Cats

Surgical Management of a Traumatic Brain Herniation Through the Bregmatic Fontanelle in a Dog

A 1 yr old female Chihuahua was presented for traumatic skull injury. Computed tomography revealed brain herniation through the bregmatic fontanelle. The hernia was manually reduced, and the defect was repaired using a polypropylene mesh. To the authors' knowledge, this is the first reported case of brain herniation through the bregmatic fontanelle in a dog.

A retrospective case-control study evaluating systemic blood pressure and heart rate in dogs with brain herniation under general anesthesia

OBJECTIVE

To examine whether increased systemic arterial blood pressure (ABP) and decreased heart rate (HR) under inhalant anesthesia were suggestive of the Cushing reflex (CR) in dogs with neurological diseases based on magnetic resonance imaging (MRI) findings.

STUDY DESIGN

Retrospective case-control study.

ANIMALS

A sample of 137 client-owned dogs admitted to two veterinary teaching hospitals for diagnosis and patient care owing to suspected intracranial disease from 2005 to 2020. All dogs underwent general anesthesia for MRI of the brain.

METHODS

Based on MRI study reports, dogs were divided into three study groups: group A, dogs with suspected brain herniation; group B, dogs with an abnormal MRI finding but without suspicion of herniation; and group C, dogs with structurally unremarkable brains (control). Initial evaluation by an anesthesiologist resulted in 58 cases selected for further review based on suspicion of having intracranial hypertension, as indicated by ABP and HR changes under anesthesia. Anesthetic records were randomized and independently reviewed by three board-certified anesthesiologists blinded to MRI diagnosis who allocated each dog into one of three groups: 1) likely to have CR; 2) unlikely to have CR; or 3) insufficient data for determination.

RESULTS

Of the 58 cases evaluated, nine were considered likely to have CR and 48 were considered unlikely to have CR. In one case, the anesthesiologists were unable to determine whether CR occurred. Of the nine dogs with likely CR, three had an MRI diagnosis of intracranial herniation. The remaining six dogs suspected of CR belonged to the normal brain group.

CONCLUSIONS AND CLINICAL RELEVANCE

The ABP and HR changes associated with CR are not reliably associated with brain herniation in dogs undergoing general anesthesia.

Multiple Meningioma Resection by Bilateral Extended Rostrotentorial Craniotomy with a 3D-Print Guide in a Cat

Simple Summary

Meningioma is the most common intracranial neoplasia in cats. Treatments for meningiomas—including complete surgical resection, debulking, irradiation, or palliative therapy—have been reported in veterinary medicine. However, multiple meningiomas (two or more meningiomas in the same patient, separated by anatomical location) have been reported to affect the complication rate and prognosis. Moreover, the characteristics of neurosurgery—such as accurate localization and awareness of the anatomical structures of the lesions—make the surgery especially difficult for inexperienced surgeons. Surgical navigation systems have been developed, but recently, patient-specific three-dimensional(3D)-printed models and guides have also been used in orthopedics and neurosurgeries for treating many disorders with good results. A 13-year-old castrated male domestic shorthair cat was referred with multiple meningiomas located within the right frontal and occipital lobes. The cat suffered from generalized tonic–clonic seizures and mild proprioceptive ataxia. After removing both of the tumors, the cat showed a favorable clinical outcome and no neurological abnormalities throughout long-term follow-up. With a patient-specific 3D guide technology, a craniotomy for multiple meningiomas can be performed safely and accurately.

Abstract

A 13-year-old castrated male domestic shorthair cat was referred for the surgical removal of multiple meningiomas. The cat experienced generalized tonic–clonic seizures, altered mentation, mild proprioceptive ataxia, and circling. Magnetic resonance imaging (MRI) revealed two round, solitary, well-delineated, space-occupying lesions suggestive of multiple meningiomas in the right frontal and occipital lobes. Before surgery, patient-specific three-dimensional (3D) printed models and guides were produced using a 3D program based on MRI and computed tomography (CT), and a rehearsal surgery was performed. With a 3D guide to find the location of the craniotomy lines, bilateral extended rostrotentorial craniotomy allowed en bloc resection of multiple meningiomas. The bone fragment was replaced and secured to the skull with a craniofacial plate and screws with an artificial dura. All of the surgical steps were performed without complications. The preoperative presenting signs were resolved by the time of follow-up examinations 2 weeks after surgery. Twelve months after the removal of the multiple meningiomas, the cat survived without further neurological progression. For the resection of multiple meningiomas, surgery can result in large bone defects and risk of massive hemorrhage. For this challenging surgery, patient-specific 3D models and guides can be effective for accurate and safe craniotomies.

Relationship between admission vitals and brain herniation in 32 cats: a retrospective study

OBJECTIVES

The aim of the study was to evaluate whether any admission vitals correlated with the presence of brain herniation diagnosed via MRI in cats presenting with neurologic signs.

METHODS

Medical records at two veterinary university referral centers were reviewed to identify cats that underwent brain MRI between 2010 and 2019. A control group of cats with intracranial lesions without concurrent brain herniation was analyzed for comparison. Data relating to signalment, vitals on admission, abnormalities observed on initial neurologic examination, underlying etiology, advanced imaging findings and outcome were reviewed. A Modified Glasgow Coma Scale (MGCS) score was determined retrospectively based on initial neurologic examination. Logistic regressions were performed to investigate the relationship between each risk factor and the odds of brain herniation as diagnosed on MRI.

RESULTS

Thirty-two cats with brain herniation and 44 cats with abnormal brain MRI without evidence of herniation (as a control group) based on MRI findings were included. Cats with intracranial neoplasia vs other diagnoses were found to be at increased risk of herniation (odds ratio [OR] 4.8, 95% confidence interval [CI] 1.8-13.8; P = 0.001). The odds of herniation increased with age (OR 1.1, 95% CI 1.01-1.2; P = 0.031). Cats with herniation had a significantly lower level of consciousness in their MGCS score (P <0.0001) than cats without herniation. There was no significant difference in either motor activity or brainstem reflexes between the groups (P >0.05).

CONCLUSIONS AND RELEVANCE

Admission heart rate and blood pressure were not associated with brain herniation. Cats with herniation were presented with a significantly lower level of consciousness in their MGCS score; however, this clinical feature cannot be directly attributable to and predictive of herniation. Older cats with intracranial neoplasia are more likely to have brain herniation.

Utility of a flexed neck sagittal magentic resonance imaging sequence for the assessment of cerebellomedullary cistern in dogs

Cerebrospinal fluid (CSF) collection from the cerebellomedullary cistern (CM) of dogs with congenital or acquired cerebellar herniation could lead to serious complications. It is anecdotally more challenging in large brachycephalic breeds possibly due to the increased distance between the skin and CM. The first objective of this study was to assess whether flexed‐neck sagittal magnetic resonance imaging (MRI) sequences would assist in the decision‐making process of collecting CSF from the CM. The second objective was to examine the dimensions of the CM measured in extended and flexed views, and whether cranial index (CI), skull height and body weight correlated with the distance of the CM from the skin surface. Forty‐one dogs of various breeds were included in the study. Measurements were performed on T2‐weighted sagittal sequences acquired in extended and flexed‐neck positions, and transverse sequences acquired in an extended‐neck position. Mild cerebellar herniation was detected in 23/41 (56%) of the flexed‐neck views versus none in the extended views. The CM area was significantly larger in flexed‐neck views than in extended views (p < 0.05). In 29% of the cases (12/41), the trajectory of the needle intersected the cerebellar vermis. There was a positive correlation between the distance of the CM from the skin and body weight (p < 0.05) and skull height (p < 0.05), but not with the CI (p = 0.23). These findings suggest that a flexed‐neck sagittal MRI sequence helps with assessment of the size of the CM and degree of cerebellar herniation, and that skull height and body weight, but not cranial index, affect the distance of the CM from the skin surface.

Retrospective evaluation of the relationship between admission variables and brain herniation in dogs (2010-2019): 54 cases

OBJECTIVE

To document the admission systolic blood pressure (SBP), heart rate (HR), and modified Glasgow coma scale (MGCS) score in dogs with and without brain herniation and to determine their relationship with brain herniation.

DESIGN

Retrospective study between 2010 and 2019.

SETTING

University veterinary teaching hospital.

ANIMALS

Fifty-four client-owned dogs with brain herniation and 40 client-owned dogs as a control group, as determined on magnetic resonance imaging.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

SBP, HR, MGCS score, and outcome were extracted from medical records. MGCS score was retrospectively calculated based on initial neurological examination in dogs with adequate available information. Dogs with brain herniation had a significantly higher SBP (P = 0.0078), greater SBP-HR difference (P = 0.0006), and lower MGCS score (P < 0.0001) compared to control dogs. A cutoff value of an SBP ≥ 178 mm Hg, SBP-HR ≥ 60, and MGCS score ≤ 14 each provides a specificity of 90%-98%. A combination of an SBP > 140 mm Hg and HR < 80/min provided 24% sensitivity and 100% specificity to diagnose dogs with brain herniation (P < 0.0001).

CONCLUSIONS

A high SBP, a greater difference between SBP and HR, a combination of higher SBP and lower HR, and a low MGCS score were associated with brain herniation in dogs presenting with neurological signs upon admission. Early recognition of these abnormalities may help veterinarians to suspect brain herniation and determine timely treatment.

Magnetic Resonance Imaging and Gait Analysis Indicate Similar Outcomes Between Yucatan and Landrace Porcine Ischemic Stroke Models

The Stroke Therapy Academic Industry Roundtable (STAIR) has recommended that novel therapeutics be tested in a large animal model with similar anatomy and physiology to humans. The pig is an attractive model due to similarities in brain size, organization, and composition relative to humans. However, multiple pig breeds have been used to study ischemic stroke with potentially differing cerebral anatomy, architecture and, consequently, ischemic stroke pathologies. The objective of this study was to characterize brain anatomy and assess spatiotemporal gait parameters in Yucatan (YC) and Landrace (LR) pigs pre- and post-stroke using magnetic resonance imaging (MRI) and gait analysis, respectively. Ischemic stroke was induced via permanent middle cerebral artery occlusion (MCAO). MRI was performed pre-stroke and 1-day post-stroke. Structural and diffusion-tensor sequences were performed at both timepoints and analyzed for cerebral characteristics, lesion diffusivity, and white matter changes. Spatiotemporal and relative pressure gait measurements were collected pre- and 2-days post-stroke to characterize and compare acute functional deficits. The results from this study demonstrated that YC and LR pigs exhibit differences in gross brain anatomy and gait patterns pre-stroke with MRI and gait analysis showing statistical differences in the majority of parameters. However, stroke pathologies in YC and LR pigs were highly comparable post-stroke for most evaluated MRI parameters, including lesion volume and diffusivity, hemisphere swelling, ventricle compression, caudal transtentorial and foramen magnum herniation, showing no statistical difference between the breeds. In addition, post-stroke changes in velocity, cycle time, swing percent, cadence, and mean hoof pressure showed no statistical difference between the breeds. These results indicate significant differences between pig breeds in brain size, anatomy, and motor function pre-stroke, yet both demonstrate comparable brain pathophysiology and motor outcomes post-stroke. The conclusions of this study suggest pigs of these different breeds generally show a similar ischemic stroke response and findings can be compared across porcine stroke studies that use different breeds.

Incidence and type of brain herniation associated with intracranial meningioma in dogs and cats

The incidence of brain herniation (BH) in association with intracranial meningioma (ICM) in dogs and cats is poorly described. The aim of this study was to evaluate the rate and type of brain herniations in client-owned dogs and cats with ICMs and to determine the meningioma volume (MV) relative to cranial cavity volume (CCV). A retrospective magnetic resonance imaging (MRI) analysis study of 24 cats and 45 dogs with ICMs was conducted to ascertain the presence and characteristics of BH. MV and CCV were measured and their ratio was calculated for each animal. Correlations of MV/CCV with independent variables were analyzed. BH was encountered in 24/24 cats (100%) and 30/45 dogs (66.7%) with ICMs. In cats, the most frequent presentation was foramenal herniation (FMH; 23/24, 95.8%), followed by caudotentorial (CTH; 21/24, 87.5%) and subfalcine (SH; 18/24, 75.0%) herniation. In dogs, the most frequent presentation was SH (28/45; 62.2%), followed by CTH (9/45; 20%) and FMH (2/45; 4.4%). Relative to dogs, cats with ICM had greater incidences of FMH (P<0.001) and CTH (P<0.001). Mean MV/CCV ratio was higher in cats (0.098) than in dogs (0.038; P<0.001). The most common clinical sign of ICM was altered behavior in cats (43%, P<0.01) and seizures in dogs (74.4%, P<0.001). In conclusion, cats were found to be more likely than dogs to present FMH and CTH, with a proportionally greater neoplasia volume.

Surgical treatment of rostrotentorial meningioma complicated by foraminal herniation in the cat

OBJECTIVES

This study was performed to evaluate retrospectively the clinical signs, complications and postoperative outcomes of feline intracranial meningioma (IM) with concurrent cingulate, transtentorial and foramen magnum herniations.

METHODS

The medical records and MRI scans of cats with IM and cerebral herniation were reviewed. Cases involving concurrent cingulate, transtentorial and foramen magnum herniations were included. Owners were contacted to obtain long-term follow-up information.

RESULTS

Seven cats (four castrated males and three spayed females) met the inclusion criteria. Median age was 13.0 years (range 9.9-16.1 years) and median duration of clinical signs was 35 days (range 21-163 days). The clinical signs of cats with cerebral herniation included visual impairment (n = 5 [71.4%]), ataxia (n = 4 [57.1%]), impaired consciousness (n = 2 [28.6%]), head pressing (n = 2 [28.6%]), paresis (n = 1 [14.3%]), torticollis (n = 1 [14.3%]) and personality changes (n = 1 [14.3%]). Median tumour volume, cranial cavity volume and tumour volume:intracranial volume ratio before surgery were 3.37 cm3 (range 3.23-11.5 cm3), 32.6 cm3 (range 29.8-78.3 cm3) and 10.4% (range 5.3-35.3%), respectively. Median overall tumour excision rate was 90.6%. Preoperative intracranial pressure (ICP) ranged from 15 to 32 mmHg (median 29 mmHg). In all cases, the ICP dropped to 0 mmHg immediately after tumour removal. No adjuvant therapy was required after surgery. The median survival period was 612 days (range 55-1453 days).

CONCLUSIONS AND RELEVANCE

The results of this study indicate that surgical treatment of rostrotentorial IM is effective and allows prolonged survival, even in cats with concurrent cingulate, transtentorial and foramen magnum herniations.

Evaluation of basilar artery and cerebrospinal fluid dynamics using phase-contrast MRI: Comparison between mannitol and isotonic saline solution

Increased intracranial pressure (ICP) can cause irreversible pathological changes in the canine brain and can be life-threatening, so prompt diagnosis and therapeutic responses are warranted. The purposes of this prospective experimental study were to evaluate phase-contrast MRI (PC-MRI) as a non-invasive method for quantifying cerebrospinal fluid (CSF) and basilar artery flow, and to assess effects of intravenous administration of hypertonic fluid. A PC-MRI scan was acquired for six healthy Beagle dogs at the level of the mesencephalic aqueduct. Either 1.0 g/kg mannitol or isotonic saline solution was administered intravenously for 15 min each at a matched dose volume of 5 mL/kg. Basilar artery and CSF flow rates were measured and their values compared between mannitol and isotonic saline solution groups before administration, and subsequently every 15 min for 2 h post-administration. The CSF dynamics were further assessed by measuring repeat flow from the caudal to rostral direction and the rostral to caudal direction as the number of waves. No significant difference was observed in basilar or and CSF flow velocity between the two groups (P > .05). However, administration of isotonic saline solution tended to increase basilar artery velocity slightly over time, while CSF velocity remained unchanged. In the mannitol group, CSF wave forms tended to be reduced at 60 and 75 min (P > .05). Findings from this preliminary study indicated that it is feasible to measure the dynamics of CSF and basilar artery flow by PC-MRI, but no flow differences could be detected for mannitol versus isotonic saline administration.

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.

Neural Stem Cell Extracellular Vesicles Disrupt Midline Shift Predictive Outcomes in Porcine Ischemic Stroke Model

Magnetic resonance imaging (MRI) is a clinically relevant non-invasive imaging tool commonly utilized to assess stroke progression in real time. This study investigated the utility of MRI as a predictive measure of clinical and functional outcomes when a stroke intervention is withheld or provided, in order to identify biomarkers for stroke functional outcome under these conditions. Fifteen MRI and ninety functional parameters were measured in a middle cerebral artery occlusion (MCAO) porcine ischemic stroke model. Multiparametric analysis of correlations between MRI measurements and functional outcome was conducted. Acute axial and coronal midline shift (MLS) at 24 h post-stroke were associated with decreased survival and recovery measured by modified Rankin scale (mRS) and were significantly correlated with 52 measured acute (day 1 post) and chronic (day 84 post) gait and behavior impairments in non-treated stroked animals. These results suggest that MLS may be an important non-invasive biomarker that can be used to predict patient outcomes and prognosis as well as guide therapeutic intervention and rehabilitation in non-treated animals and potentially human patients that do not receive interventional treatments. Neural stem cell–derived extracellular vesicle (NSC EV) was a disruptive therapy because NSC EV administration post-stroke disrupted MLS correlations observed in non-treated stroked animals. MLS was not associated with survival and functional outcomes in NSC EV–treated animals. In contrast to untreated animals, NSC EVs improved stroked animal outcomes regardless of MLS severity.

Comparison of medical and/or surgical management of 23 cats with intracranial empyema or abscessation

OBJECTIVES

Feline intracranial abscessation or empyema is infrequently reported in the veterinary literature. To date, the largest study is based on a population of 19 cats with otogenic infection. The aim of this study was to review a larger population of cats with intracranial empyema from multiple aetiologies and document their signalment, imaging findings, treatment protocols (including medical and/or surgical management) and to compare outcomes.

METHODS

Cases presenting to a single referral centre over a 10 year period with compatible history, neurological signs and imaging findings consistent with intracranial abscessation and empyema were reviewed retrospectively.

RESULTS

Twenty-three cats met the inclusion criteria. Advanced imaging (CT and/or MRI) was performed in 22/23 cats; one case was diagnosed via ultrasound. Ten cases underwent medical and surgical management combined, 10 underwent solely medical management and three were euthanased at the time of diagnosis. Short-term outcome showed that 90% of surgically managed and 80% of medically managed cats were alive at 48 h post-diagnosis. Long-term survival showed that surgically managed cases and medically managed cases had a median survival time of 730 days (range 1-3802 days) and 183 days (range 1-1216 days), respectively. No statistical significance in short- or long-term survival ( P >0.05) was found between medically and surgically managed groups.

CONCLUSIONS AND RELEVANCE

Feline intracranial abscessation and empyema are uncommon conditions that have historically been treated with combined surgical and medical management. This study documents that, in some cases, intracranial abscessation and empyema can also be successfully treated with medical management alone.

Feline meningioma with extensive nasal involvement

Case summary

A 9-year-old male neutered domestic longhair cat was presented with a 3 week history of lethargy and pain of unknown origin. A large extra-axial mass was demonstrated on MRI of the head, with cribriform plate destruction, extensive nasal invasion and intracranial expansion, producing a severe mass effect. The mass was isointense on T1-weighted imaging, predominantly hypointense with some hyperintense areas on T2-weighted imaging and fluid attenuation inversion recovery, markedly contrast enhancing, and caused transtentorial and cerebellar herniation. Histopathological evaluation confirmed a transitional (mixed) meningioma.

Relevance and novel information

To our knowledge this is the first report of a meningioma with extensive nasal involvement in a cat. Based on this case, meningioma should be considered as a differential diagnosis for tumours involving the nasal cavity and frontal lobe with cribriform plate destruction.