From the Guidelines
Right hippocampal volume loss in a patient with seizure disorder is a critical finding that suggests mesial temporal sclerosis (MTS), a common cause of temporal lobe epilepsy, and indicates a potential need for surgical intervention. This finding is highly significant as it indicates that the hippocampus has undergone atrophy, likely due to recurrent seizures or an initial precipitating injury such as febrile seizures, infection, or trauma 1. Patients with this finding typically experience focal seizures with impaired awareness that may include automatisms, memory disturbances, or sensory phenomena like unusual smells. The right-sided location may correlate with non-verbal memory deficits rather than language problems (which are more common with left hippocampal involvement) 1.
Clinical Implications
The diagnosis of MTS is crucial in guiding treatment decisions, as patients with this condition often have drug-resistant epilepsy that may respond well to surgical intervention such as selective amygdalohippocampectomy or anterior temporal lobectomy 1. According to the most recent guidelines, epilepsy surgery is a promising option for patients with drug-resistant focal epilepsy, with approximately 65% of patients becoming seizure-free 1.
Diagnostic Approach
To confirm the diagnosis and assess the extent of hippocampal damage, a comprehensive diagnostic approach is necessary, including:
- High-resolution MRI with coronal T1-weighted imaging perpendicular to the long axis of the hippocampus
- Neuropsychological testing to assess memory function
- Evaluation for surgical candidacy if medications fail to control seizures 1
- Consideration of molecular neuroimaging with interictal [18 F]fluorodeoxyglucose ([18 F] FDG) positron emission tomography (PET) or ictal subtraction perfusion SPECT to localize the seizure onset zone 1
Treatment Considerations
The underlying pathophysiology of MTS involves neuronal loss and gliosis in the hippocampus, which creates a hyperexcitable neural network that generates seizures. Treatment should focus on controlling seizures and improving quality of life, with surgical intervention considered for patients with drug-resistant epilepsy 1.
From the Research
Significance of Right Hippocampal Volume Loss
- Right hippocampal volume loss is a significant finding in patients with seizure disorders, particularly those with temporal lobe epilepsy 2, 3.
- Hippocampal sclerosis, which is often associated with right hippocampal volume loss, is a common cause of drug-resistant epilepsy in adults 3.
- The cause of hippocampal sclerosis is multifactorial and may involve febrile seizures, genetic susceptibility, inflammatory, and neurodevelopmental factors 4.
Clinical Implications
- Right hippocampal volume loss can be an indicator of hippocampal sclerosis, which is a diagnostic entity in mesial temporal lobe epilepsy 2.
- Patients with right hippocampal volume loss may benefit from early evaluation for epilepsy surgery, as postoperative results concerning seizures and neuropsychological outcomes are encouraging 2.
- The presence of dual pathology, such as mild to moderate cortical dysplasia, does not necessarily portend poor postsurgical outcome 5.
Comorbidities and Hippocampal Volume Loss
- Depression is a common comorbidity in patients with chronic epilepsy, and its effects on hippocampal volume are unknown 6.
- Higher degrees of hippocampal symmetry were associated with higher levels of depression in patients with right hippocampal sclerosis, suggesting that depression may influence left hippocampal volume in these patients 6.
Diagnostic and Therapeutic Considerations
- MRI and histopathology are essential diagnostic tools for evaluating hippocampal sclerosis and right hippocampal volume loss 2, 4, 5.
- Antiepileptic medication is indicated as a first-line treatment, and epilepsy surgery may be considered in medically intractable cases 2.
- Alternative procedures, such as stereotactic radiofrequency amygdalohippocampectomy and hippocampal stimulation, are being assessed as potential therapeutic options 2.