The interseptal distance (ISD) is a measurement used to assess septal area atrophy as a marker for neurodegenerative conditions in patients with memory problems 1.
It is proposed that atrophy of the septal nuclei can commonly be seen in conditions associated with hippocampal atrophy, particularly in Alzheimer disease (AD) 2. It can also be seen following head injury or in chronic alcohol excess.
A widening of the interseptal distance, defined as the minimal distance between the septal nucleus of each hemisphere, has been shown to act as a surrogate marker for atrophy within core regions implicated in Alzheimer disease 1.
The interseptal distance can be accurately measured at the level of the AC-PC (anterior commissure to posterior commissure) line, i.e. the distance between the medial convexities of the septal nuclei, posterior to the anterior cerebral arteries.
It has been demonstrated that an interseptal distance greater than or equal to 4 mm has a good predictive power for patients with memory problems. A cut-off of 4 mm gives a sensitivity of 85.7% and a specificity of 85.8%. The interseptal distance can be used to help select patients for further investigation 1.
- Gan, C., O'Sullivan, M., Metzler-Baddeley, C. and Halpin, S. (2017). Association of imaging abnormalities of the subcallosal septal area with Alzheimer's disease and mild cognitive impairment.
- Callen, D., Black, S., Gao, F., Caldwell, C. and Szalai, J. (2017). Beyond the hippocampus: MRI volumetry confirms widespread limbic atrophy in AD.