The "round the houses" sign and "zig-zag" sign in progressive supranuclear palsy and other conditions

A smart tool for non expert clinicians for the dissemination of the MDS criteria for progressive supranuclear palsy

Due to the variety of clinical phenotypes and the massive clinical overlap with other neurodegenerative diseases, the diagnosis of Progressive Supranuclear Palsy (PSP) remains a major challenge. Notwithstanding, early and reliable clinical diagnosis of PSP is highly warranted for estimation of prognosis, appropriate allocation to therapeutic trials and development of new diagnostic tools. As reliable biomarkers are lacking, PSP diagnosis relies on the application of the clinical criteria promoted by the International Parkinson and Movement Disorder Society (MDS). Despite providing a framework including all the main PSP cornerstones (ocular dysfunction and postural instability, akinesia and cognitive dysfunction), the application of the MDS PSP criteria is complex and not straightforward to apply in a clinical setting. Herein we propose a practical tool, including a video-guided slide-set and a smartsheet, to disseminate the MDS PSP clinical criteria among healthy practitioners and increase confidence in non expert clinicians towards suspicion and diagnosis of PSP. The video-guided slide set may serve as a teaching resource for both general neurologists and practitioners, while the smartsheet may represent a valid support in attributing the degree of diagnostic certainty and phenotype based on the identified clinical features. Application of our tool may improve early recognition of patients in primary and secondary care and determine a prompt referral to third level movement disorder centers for consideration in clinical trials testing disease-modifying treatments.

Detecting Abnormal Eye Movements in Patients with Neurodegenerative Diseases - Current Insights

This review delineates the ocular motor disturbances across a spectrum of neurodegenerative disorders, including Alzheimer's Disease (AD) and related disorders (ADRD), Parkinson's Disease (PD), atypical parkinsonism, and others, leveraging advancements in eye-tracking technology for enhanced diagnostic precision. We delve into the different classes of eye movements, their clinical assessment, and specific abnormalities manifesting in these diseases, highlighting the nuanced differences and shared patterns. For instance, AD and ADRD are characterized by increased saccadic latencies and instability in fixation, while PD features saccadic hypometria and mild smooth pursuit impairments. Atypical parkinsonism, notably Progressive Supranuclear Palsy (PSP) and Corticobasal Syndrome (CBS), presents with distinct ocular motor signatures such as vertical supranuclear gaze palsy and saccadic apraxia, respectively. Our review underscores the diagnostic value of eye movement analysis in differentiating between these disorders and also posits the existence of underlying common pathological mechanisms. We discuss how eye movements have potential as biomarkers for neurodegenerative diseases but also some of the existing limitations.

Central Ocular Motor Disorders: Clinical and Topographic Anatomical Diagnosis, Syndromes and Underlying Diseases

The key to the diagnosis of ocular motor disorders is a systematic clinical examination of the different types of eye movements, including eye position, spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, as well as testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR. This is like a window which allows you to look into the brain stem and cerebellum even if imaging is normal. Relevant anatomical structures are the midbrain, pons, medulla, cerebellum and rarely the cortex. There is a simple clinical rule: vertical and torsional eye movements are generated in the midbrain, horizontal eye movements in the pons. For example, isolated dysfunction of vertical eye movements is due to a midbrain lesion affecting the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), with impaired vertical saccades only or vertical gaze-evoked nystagmus due to dysfunction of the Interstitial nucleus of Cajal (INC). Lesions of the lateral medulla oblongata (Wallenberg syndrome) lead to typical findings: ocular tilt reaction, central fixation nystagmus and dysmetric saccades. The cerebellum is relevant for almost all types of eye movements; typical pathological findings are saccadic smooth pursuit, gaze-evoked nystagmus or dysmetric saccades. The time course of the development of symptoms and signs is important for the diagnosis of underlying diseases: acute: most likely stroke; subacute: inflammatory diseases, metabolic diseases like thiamine deficiencies; chronic progressive: inherited diseases like Niemann-Pick type C with typically initially vertical and then horizontal saccade palsy or degenerative diseases like progressive supranuclear palsy. Treatment depends on the underlying disease. In this article, we deal with central ocular motor disorders. In a second article, we focus on clinically relevant types of nystagmus such as downbeat, upbeat, fixation pendular, gaze-evoked, infantile or periodic alternating nystagmus. Therefore, these types of nystagmus will not be described here in detail.