Korean Journal of
Veterinary Service

Traumatic brain injury (TBI) occurs when an external force impacts the brain (Dos Santon LO et al, 2018). Various incidents can cause TBI, including falls, motor vehicle collisions, sports-related injuries, or physical assault (Sande and West, 2010). Not all individuals sustaining a head injury will necessarily have a poor prognosis. According to a retrospective study, over 80% of individuals with blunt trauma survived (Simpson et al, 2009). To assess the prognosis in dogs with TBI, computed tomography (CT) or magnetic resonance imaging (MRI) may be helpful (Beltran et al, 2014). In this report, two dogs underwent CT imaging, while one underwent MRI.

A 7-year-old (4.0 kg) neutered male Chihuahua (case 1) was presented following a motor vehicle collision, exhibiting seizures. Physical examination revealed a rectal temperature of 37.1℃, heart rate of 96 bpm, respiratory rate of 102 per minute, systolic blood pressure of 130 mmHg, and left ocular hyperemia. Neurological examination showed no bilateral menace response. Laboratory tests indicated mild hypokalemia (potassium, 3.75 mmol/L), hyperlactatemia (lactate, 2.7 mmol/L), elevated ALT (750 U/L), and CRP (2.5 mg/dL).CT revealed no brain abnormalities but indicated a hypodense lesion in the right parietal lung (Fig. 1). The dog was diagnosed with traumatic brain injury and pulmonary hemorrhage, however, aspiration pneumonia could not be ruled out. Treatment included UDCA (10 mg/kg PO q 12 h), silymarin (10 mg/kg PO q 12 h), biphenyl dimethyl dicarboxylate, levetiracetam (30 mg/kg IV q 12 h), vitamin K, amoxicillin clavulanic acid (22 mg/kg IV q 12 h), and enrofloxacin (10 mg/kg IV q 24 h). After three days, ALT decreased to 537 U/L, CRP improved to 0.9 mg/dL, and the menace response partially recovered. The dog was discharged with levetiracetam (30 mg/kg PO q 12 h). In addition, mannitol (1 g/kg IV) was administered as decompressive therapy, and three weeks later, all of clinical signs were completely resolved.

Figure 1. CT images of the Case 1 dog. No significant intracranial hemorrhage was observed (a, b). Lesions suspected to be lung collapse and/or hemorrhage were detected in the left posterior lung (c) and the right anterior lobe of the lung (d).

A 1-year-old (15 kg) spayed mixed-breed dog (case 2) was transferred after a head injury. Initial treatment with mannitol was given. Upon transfer, decreased pupillary light reflex (PLR) was noted in the left eye. Physical examination showed a body condition score of 4/9, rectal temperature of 39.2℃, heart rate of 142 bpm, and systolic blood pressure of 110 mmHg, with subconjunctival hemorrhage in the left eye. Laboratory tests, including CBC and electrolyte analysis, were normal. CT revealed a hyperdense lesion in the left piriform lobe and decreased density in the cerebellum and temporal lobe (Fig. 2). The dog was diagnosed with traumatic brain injury and secondary PLR decrease. Mannitol (1 g/kg IV) was administered, and the dog fully recovered after transfer to a local hospital.

Figure 2. CT images of the Case 2 dog. A biconvex high-density area in the left piriform lobe and slight contrast enhancement were detected in the lesion (a, b). No significant skull fracture or nasal bleeding was observed (c∼f). The patient was tentatively diagnosed with epidural hemorrhage.

A 10-month-old (3.0 kg) intact female Maltese (case 3) was referred after falling from a chair, presenting with a dazed state, excessive salivation, and counterclockwise circling. Physical examination showed a body condition score of 5/9, rectal temperature of 39.0℃, heart rate of 150 bpm, and systolic blood pressure of 130 mmHg. Neurological examination revealed a lack of menace response in the right eye and no response in the right hind limb. Laboratory tests showed mild neutrophilia (12,300/uL) and mild monocytosis (1,400/uL), with normal CRP and serum chemistry. MRI revealed T2/FLAIR hyperintense areas in the left cerebral hemisphere and thalamus, suggesting a midline shift and possible hemorrhage (Fig. 3). The dog was diagnosed with traumatic brain injury. Despite decompressive treatment with mannitol (0.5∼1 g/kg IV for 3 days), symptoms worsened, leading to euthanasia one month later.

Figure 3. MRI images of the Case 3 dog. High T2/FLAIR signals were detected around the left cerebral hemisphere, on the frontal lobe, parieto-temporal lobe, and occipital lobe (a∼d).

In human medicine, prognosis for patients with TBI is often predicted using the modified Glasgow coma scale (MGCS) (Bae et al, 2019). Similarly, in dogs with TBI, clinical evaluation includes assessment of the MGCS score, which measures motor response, brainstem reflexes, and consciousness level (Platt et al, 2001). The patient’s total MGCS score is calculated by summing the scores of each category, ranging from 1 to 6. The total MGCS score ranges from 3 to 18, with the lowest score indicating the most severe neurological impairment and the lowest likelihood of survival within the initial 48 hours following head trauma (Platt et al, 2001). However, there is increasing acknowledgment that relying solely on the Glasgow Coma Scale for predicting outcomes in humans after TBI is highly limited (Zuercher et al, 2009). Recent research has emphasized CT and MRI findings as prognostic indicators due to their sensitivity in identifying nonhemorrhagic contusions, diffuse axonal injuries, and brainstem lesions (Skandsen et al, 2011; Chew et al, 2012; Hilario et al, 2012; Lee et al, 2012; Shenton et al, 2012; Yuh et al, 2013).

According to one study, there was a significant negative correlation between the location and severity of lesions and the MRI grade, degree of midline shift, and percentage of intraparenchymal lesion among cases in relation to prognosis (Beltran et al, 2014). Based on the scoring system introduced in the previous study (Beltran et al, 2014), there were lesions in the right frontal, parietal, and temporal lobes, corresponding to grade 3 in case 3. Furthermore, brain edema, midline shift due to inflammation, and lesions involving more than 50% of the white matter in the left cerebral frontal lobe, 25∼50% in the parietotemporal lobe, and 25∼50% in the occipital lobe were also observed. Consequently, the patient was anticipated to have a poor prognosis, and indeed, symptoms deteriorated, leading to euthanasia one month later.

Prognostic evaluation of CT scans in dogs with head trauma can include scoring hemorrhage, midline shift or lateral ventricle asymmetry, cranial vault fracture, and depressed fracture or infratentorial lesion from 0 to 7 based on the presence of hypodensity, hemorrhage, and fracture lesions. Higher scores indicate a worse prognosis (Chai et al, 2017). In case 1, there was no evidence of skull fracture, hemorrhage, or other significant findings besides lung collapse, hemorrhage, and otitis media, resulting in a score of 0. Similarly, case 2 also scored 0 due to the absence of skull fracture, hemorrhage, or other significant findings except for minimal contrast enhancement in the left cerebral piriform lobe. Based on the scoring, both cases were expected to have favorable short-term and long-term prognoses, and indeed, symptoms improved in both cases.

Imaging evaluation using CT or MRI in dogs with traumatic brain injury can assist clinicians in accurately assessing the prognosis of these patients.

This study was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MSIT) (RS-2023-00252033).

No potential conflict of interest relevant to this article was reported.