Case presentationAn 8 year old female neutered Boxer presented with a history of recent onset generalised seizures. Physical and neurological examinations were unremarkable.
Question. What is your neurolocalisation?Question. What are your most likely differentials?
For further investigations, imaging, diagnosis and the answers to these questions, please scroll down the page.
Question. What is your neurolocalistion?Answer. Seizures suggest forebrain disease.
Question. What are your most likely differentials?Answer. The breed and age are suggestive of neoplasia. Other differentials include metabolic disease, immune-mediated disease, infectious disease and late onset idiopathic epilepsy.
Further investigationsRoutine haematology, biochemistry and protozoal serology were unremarkable. MRI of the brain was performed (fig 1.) which showed a poorly contrast enhancing mass, which was bright on T2, in the left forebrain.
Fig 1. T2 weighted transverse MRI scan of brain. There is a large hyperintense mass in the left cerebral hemisphere, which is showing some mass effect as evidenced by compression of the lateral ventricle. Note the black shadow in the bottom left of the picture, which is artefact due to the metal spring in the cuff of the endotracheal tube.
DiagnosisBrain tumour
Question: What is the likely type of tumour, and what is the best treatment?
For the answer to this question, please scroll down the page.
Question. What is the likely type of tumour, and what is the best treatment?Answer. Boxers are prone to develop gliomas. They can also get meningiomas, but these tend to have a good, homogenous contrast uptake, whereas gliomas usually poorly enhance or show a ring enhancement. Histopathology is necessary to be certain of the diagnosis however. Gliomas are invasive tumours and surgical removal is rarely indicated. Treatment options include palliation with steroids to reduce peritumoural oedema, chemotherapy with lomustine, and radiotherapy. Radiotherapy is generally well tolerated, and can lead to durable remissions.
Treatment and follow upTreatment consisted of radiotherapy plus phenobarbitone. Seizures resolved, and the phenobarbitone was weaned off.
MRI was performed 6 months after the radiotherapy which showed the tumour was no longer evident (see fig 2).
Fig 2. T2 weighted transverse MRI of the same Boxer as in figure 1, 6 months after radiotherapy.
DiscussionBoxers are strongly predisposed to develop gliomas, and Boxers that develop seizures, even if they are less than 6 years old, should be considered for MRI imaging to aid in reaching a diagnosis. There are several treatment options, but radiotherapy, where available, probably gives the longest survival times, and is usually well -tolerated.
As with all imaging, histopathology is usually required to make a definitive diagnosis. However, there are some characteristics that help distinguish between glioma and cerebrovascular accident. I recommend the paper Cervera et al in Vet Radiology and Ultrasound from Jan 2011 for more information. To quote from the abstract:
"Gliomas were predominantly located in the cerebrum (76%) compared with presumed cerebrovascular accidents that were located mainly in the cerebellum, thalamus, caudate nucleus, midbrain, and brainstem (76%). Gliomas were significantly larger compared with presumed cerebrovascular accidents and more commonly associated with mass effect and perilesional edema. Wedge-shaped lesions were seen only in 19% of presumed cerebrovascular accidents. "
However, it does also report that:
"Between the three observers, 10-47% of the presumed cerebrovascular accidents were misdiagnosed as gliomas, and 0-12% of the gliomas were misdiagnosed as cerebrovascular accidents. "
However, the breed and age make neoplasia and particularly glioma high on the differential list.
Regarding treatment, unfortunately the evidence base in veterinary medicine is currently poor (part in fact hindered by the fact that many published studies don't include histopathological confirmation of the masses treated). You are correct that in humans gliomas are often treated surgically, but that is in combination with chemotherapy and radiotherapy. We studied the human approach in a little detail in my human neuroimaging course. Sadly, despite advances in treatment involving such things as intra-operative MRI, with real-time representation of the surgical tools during the procedure within the MRI, in order to as accurately as possible remove tumour and not healthy tissue, the prognosis for high grade gliomas in humans remains very poor. There is a lot of anecdotal information regarding treatment of brain tumours in dogs. At the BSAVA Masterclass on brain tumours in 2009, Peter Dickinson said that for treatment of canine glioma, almost all data is anecdotal. The value of surgical resection, radiotherapy or chemotherapy has not been demonstrated. Radiation therapy appears to be beneficial, but the actual benefit is unknown. Lomustine is indeed the treatment of choice for gliomas (it is hydroxyurea for meningiomas) if using chemotherapy, see for example Mariani 2003, ACVIM conference proceedings on emerging treatment for gliomas.
The word "durable" was used deliberately because the evidence base is poor. However, see below for an overview of the literature.
The protozoal infections we tend to look for in the UK when investigating neurological diseases are toxoplasma and neospora.
I hope you find that information useful.
Authors
Tumor type
No.
Treatment
Median survival in weeks (range)
Turrel et al., 1984
All
8
Symptomatic
8 (1.4-44)
Foster et al., 1988
43
8 (mean) (0.1-58)
Heidner et al., 1991
45
0.8 (N/R)
Niebauer et al., 1991
All except meningiomas
10
Surgery (+/- radiation/chemotherapy)
59 (N/R)
16
Surgery (1 dog also received 125I)
3.9 (N/R)
4
Radiation (36Gy)
46 (25-71)
Norman et al., 1997
26
Radiation (39Gy)
33 (8.8-240+)
Brearly et al., 1999
83
Radiation (38Gy) (11 dogs had surgery)
43.7(0.1-172+)
Spugnini et al., 2000
29
Radiation (48Gy, one dog 54Gy)
35.7 (3-115)
25
Radiation (45.6-48Gy, +/-hyperthermia, +/- surg.)
34.3 (N/R)
Evans et al., 1993
14
Radiation (39-45Gy + surgery in 3 dogs)
70 (3-179)
Thrall et al., 1999
Radiation + WBH
21.8 (N/R)
Fulton et al 1990
7
CCNU +/- surgery
28 (4-120+)
Dimski et al, 1990
Astrocytoma
1
BCNU
28
Kostolich et al, 1987
Meningioma (olfact. bulb)
Surgery
19 (9-29)
Meningioma
28 (N/R)
Extra-axial tumor
35
Radiation (38Gy)
49.3(N/R)
6
Surgery and radiation (38Gy)
63.4(N/R)
Théon et al., 2000
20
Surgery and radiation (48Gy)
120 (N/R)
Intra-axial tumor
40.4(N/R)
5
Surgery +/- radiation (38Gy)
43.7(N/R)
Have you ruled out brain haemorrhage? can we see the GE sequence? Can we see the T1WPC? "recent onset seizure episodes": what does it mean? did the dog have sudden onset seizure/cluster seizures...?
This statement: "... surgical removal is rarely indicated": who said that? It's an interesting statement and goes against human medicine actually.
This statement: "Treatment options include [] chemotherapy with lomustine.. Who said that? maybe you were speaking about meningiomas??
This statement: "Radiotherapy is generally well tolerated, and can lead to durable remissions" it's another interesting statement: what does it mean "durable"? Months, days.. years??
You were looking for protozoal infection before the MRI scan or after? Which protozoa were you looking for?