Describe the early symptoms and propose a unifying nomenclature and criteria for right-predominant temporal lobe degeneration.

To date, the clinical profile of right-predominant temporal lobe neurodegeneration remains elusive. We performed an in-depth analysis of 19 patients with right temporal variant and an autopsy diagnosis of frontemporal lobar degeneration(FTLD)[FTLD-TDP type-C (n=13); FTLD-TDP type-A due to progranulin mutation(n=2);Pick`s disease(n=4)].  

We evaluated the clinical and behavioral profile of an autopsy confirmed series of patients given any of the following diagnoses during life: Right-temporal semantic-variant primary progressive aphasia(svPPA), right-temporal behavioral-variant frontotemporal dementia(bvFTD), or right semantic dementia(SD). Voxel-based morphometry was used to assess gray matter atrophy.

The most common first, second and third symptoms were loss of empathy(68%,n=13/19), loss of person, object and language-related knowledge(63%,n=12/19) and compulsive behavior(42%,n=8), respectively. Neuropsychological testing revealed impairment in executive and memory domains (Trails and CVLT -3.7 and -2.9 SD below the mean (btm),respectively). Semantic and verbal fluencies were -3SD and -2SD btm, respectively). Naming on BNT was(-12SD btm), comprehension on PPVT was(-12SD btm), non-verbal semantics on Pyramid and Palm Trees-Pictures was(-22SD btm), famous faces naming and familiarity were(-3.8SD and -3.4SD btm, respectively). Affect matching on CATS was(-3.8SD btm). Visuospatial systems were spared; Benson figure copy(-1SD), VOSP(0.2SD) btm. Impaired emotional and cognitive empathy on IRI-EC and PT(-2.4SD and -2.8SD btm, respectively), decreased warmth on IAS at(-17SD btm), and difficulty understanding complex emotions and social cues on TASIT-EE, SI-M for Sincere and Sarcastic were(-0.7SD, -0.1 and -9 SD btm, respectively). Early in the disease course, patients did not fulfill the current diagnostic criteria for either bvFTD or svPPA but showed a combination of features spanning both and had loss of person-specific knowledge.

Right temporal lobe degeneration presents with distinct early clinical and neuroimaging findings and has high clinical-pathological predictive specificity. A unified nomenclature and diagnostic criteria could help with early diagnosis.