MTA index: a simple 2D-method for assessing atrophy of the medial temporal lobe using clinically available neuroimaging

Abstract

Background and purpose: Despite a strong correlation to severity of AD pathology, the measurement of medial temporal lobe atrophy (MTA) is not being widely used in daily clinical practice as a criterion in the diagnosis of prodromal and probable AD. This is mainly because the methods available to date are sophisticated and difficult to implement for routine use in most hospitals—volumetric methods—or lack objectivity—visual rating scales. In this pilot study we aim to describe a new, simple and objective method for measuring the rate of MTA in relation to the global atrophy using clinically available neuroimaging and describe the rationale behind this method.Description: This method consists of calculating a ratio with the area of 3 regions traced manually on one single coronal MRI slide at the level of the interpeduncular fossa: (1) the medial temporal lobe (MTL) region (A); (2) the parenchima within the medial temporal region, that includes the hippocampus and the parahippocampal gyrus—the fimbria taenia and plexus choroideus are excluded—(B); and (3) the body of the ipsilateral lateral ventricle (C). Therefrom we can compute the ratio “Medial Temporal Atrophy index” at both sides as follows: MTAi = (A − B)× 10/C.Conclusions: The MTAi is a simple 2D-method for measuring the relative extent of atrophy in the MTL in relation to the global brain atrophy. This method can be useful for a more accurate diagnosis of AD in routine clinical practice. Further studies are needed to assess the usefulness of MTAi in the diagnosis of early AD, in tracking the progression of AD and in the differential diagnosis of AD with other dementias.

COPPADIS-2015 (COhort of Patients with PArkinson’s DIsease in Spain, 2015), a global –clinical evaluations, serum biomarkers, genetic studies and neuroimaging– prospective, multicenter, non-interventional, long-term study on Parkinson’s disease progression

“…A top priority at present in PD is to identify a diagnostic and prognostic biomarker [ 42 , 43 ]. In COPPADIS-2015, different molecular markers in blood will be evaluated (S-100b protein, TNF-ɑ, IL-1, IL-2, IL-6, vitamin B12, methylmalonic acid, homocysteine, uric acid, C-reactive protein, ferritin and iron) [ 44 – 57 ], and genetic studies (DNA and RNA) [ 58 ], and cranial MRI (MTAi, volumetry and tractography) [ 30 , 59 – 65 ] will be performed in a subgroup of patients and controls. We will try to identify markers with diagnostic and/or prognostic value, either alone or in combination (clinical and/or paraclinical).…”

“… 10) To perform genetic studies on DNA and RNA extracted from the lymphocytes of peripheral blood samples. 11) To study the possible value of a recently proposed imaging marker (MTAi) [ 30 ] to detect cognitive alterations in patients with PD and to compare it against a control group. 12) To perform volumetric imaging and tractography studies to find correlations, under plausible hypotheses, between the neuroimaging parameters and the clinical or neuropsychiatric variables and/or other variables covered in this study [ 59 – 61 ].…”

“…Volumetric (spoiled gradient recalled sequence; TR 8,5 ms, TE 4 ms, flip angle 8°, FOV 240 × 240 mm 2 , thickness 1 mm, matrix 288 × 288, voxel size 0.84 mm 3 ) and tractography (echo-planar imaging; TR 9.500 ms, TE 73 ms, FOV 224, thickness 2 mm, matrix 128 × 128, b-factors of zero and 700 s/mm 2 ) studies will be performed. Also, the Medial Temporal Atrophy Index (MTAi) [ 30 ] will be calculated. The MRI study will be performed no longer than 6 months after the first clinical assessment.…”

Manual Planimetry of the Medial Temporal Lobe Versus Automated Volumetry of the Hippocampus in the Diagnosis of Alzheimer's Disease

“…Planimetric measures are based on the area of ROIs measured on one single MRI slice. Several planimetric measures have proven to be easy to use in a clinical setting and to have good reproducibility [ 26 - 28 ]. Importantly, both the linear and the planimetric measures have the potential to be applied to computed tomography (CT) images, the most widely available imaging technique in primary health care, where most of the dementia evaluations take place [ 29 ]; it is often the first requested neuroimaging technique for routine assessment in many specialized centers.…”

Biomarkers in neurodegenerative disorders: translating research into clinical practice

“…There are two neuroimaging methods reports. One proposes the use of viscous fluid registration in voxel based morphometry studies to enhance sensitivity and localizing power in the software package SPM (Pereira et al, 2013 ) and the other describes the Medial Temporal Atrophy index (MTAi), a simple planimetric method for measuring the relative extent of atrophy of the Medial Temporal Lobe (MTA) in relation to the global brain atrophy (Menéndez-González et al, 2014a ). Following with simple methods for assessing MTA in the clinical setting, researchers from Florida describe the utility of age-specific cut-offs for visual rating of medial temporal atrophy in classifying Alzheimer's disease, MCI, and cognitively normal elderly subjects (Duara et al, 2013 ).…”