Purpose:
NPC is a progressive disorder of intracellular sterol metabolism characterised by first vertical, then horizontal ophthalmoplegia. Peak horizontal saccadic velocity was used to assess treatment response (Patterson et al, 2007). Since neuropathology is widespread in NPC we examined a range of saccade measures with regard to disease severity and brain structural integrity. Since pathology ranges from cortex to brainstem, both low-level and cognitive saccade parameters may correlate with severity scales and with multiple MRI-based volumetric measures.
Methods:
9 adult NPC patients assessed and data on illness duration and severity obtained (Iturriaga et al 2006). Reflexive saccades, antisaccades and self-paced saccades recorded. T1-weighted MRI scans acquired in a 1.5T scanner. Illness and brain volumetric measures correlated with reflexive saccade gain and latency, peak velocity, antisaccade error rate and self-paced saccades/30s.
Results:
Brainstem (gain, Vmax) and cortical (antisaccade, self-paced) measures significantly correlated with illness and structural variables. Total grey matter correlated only with self-paced rate. Not total white matter but callosal measures correlated with Vmax, gain, and self-paced saccades (Walterfang et al, in press). Latency was uncorrelated.
Conclusions:
Vmax and gain fall strongly with duration and severity of illness and likely reflect pontine pathology but negative correlations with the pons/midbrain ratio may reflect overall decline. Of the frontal measures, antisaccade error rate correlated only with illness measures; self-paced rate related inversely to illness score and positively to all structural measures except total white matter. Callosal measures may reflect integrity of frontal connections. Saccades may both reflect disease progression and be a tool to assess treatment response across the brain.
Keywords: eye movements: saccades and pursuits • neuro-ophthalmology: cortical function/rehabilitation • eye movements: conjugate