An eye tracking test (ETT), saccade, optokinetic nystagmus (OKN) test and optokinetic-after nystagmus (OKAN) test are the visual stimulation tests most commonly performed. In this article, I will examine the methods, interpretation of the results and pitfalls of those tests. The function of smooth pursuit is evaluated in an ETT. Smooth pursuit is very susceptible to central nervous system damage. Because smooth pursuit is easily affected by the age and arousal, these conditions should be considered in evaluating the results of an ETT. In saccade, the latent time, maximal eye speed and accuracy are evaluated. Saccade may be occasionally the only test that can detect the failure of the central nervous system. OKN is divided into two types by the instructions to the examinees. When examinees are instructed to look at the stripes so as to count them, one by one, OKN is Schau-Nystagmus. When examinees are instructed to stare vacantly in front of them, OKN is Stier-Nystagmus. Schau-Nystagmus differs significantly from Steir-Nystagmus in terms of the speed and form of nystagmus. It is important to clarify the instructions given to the patient. In a qualitative analysis of OKN, nystagmus are superimposed over the stripes with a computer and pursuit movements and catching movements of the target are separately examined. OKN is able to be evaluated in detail in a qualitative analysis, whereas the optokinetic pattern test (OKP) is a clinically convenient method for visually detecting slow and fast phase asymmetry of OKN. OKAN has been thought to be concerned with the velocity storage mechanism. Therefore OKAN test is significant in the study of the function of the peripheral and central vestibular system.
We tried a new therapeutic method for the lateral canal type benign paroxysmal positional vertigo (BPPV) (cupulolithiasis type) on the assumption that it was the recalcitrant type. First, we performed head stimulation in a bed type massage device (QZ-220), used under the insurance system as anti-inflammation anodyne treatment in an orthopedics setting. Following this we treated the patients with the Brandt-Daroff method. Twenty-five patients with the lateral canal type BPPV (cupulolithiasis type) underwent this treatment, and the nystagmus and the subjective symptoms disappeared in an average of 5.3±5.2 days. This was short in comparison with the subjective symptoms disappearance rate for patients in Kumamoto for whom physiotherapy was not enforced, as we reported previously. We believed that this treatment was effective for the lateral canal type BPPV (cupulolithiasis type) which was considered to be recalcitrant.
Although the duration of benign paroxysmal positional vertigo (BPPV) is generally short, it can sometimes be long and intractable. We report on a case of intractable BPPV in which the duration of disease was four years. The patient was a 38-year-old woman. She had suffered from bilateral hearing loss since childhood. Since October 2005, she experienced severe vertigo whenever she turned her head. She had consulted other doctors, but the symptoms persisted. On June 20, 2007, she was referred to the Otolaryngology Department of Tachikawa General Hospital. The positional nystagmus test demonstrated apogeotropic nystagmus in a bilateral position with a duration of more than one minute. Upbeat nystagmus with a clockwise direction (from the examiner) was seen in sitting position using the Dix-Hallpike method. A pure tone audiogram showed high tone damage causing sensorineural hearing loss bilaterally. A caloric test did not show canal paresis. Magnetic resonance imaging (MRI) of the brain showed normal findings. MRI of the inner ears showed narrowing throughout the entire semicircular canal bilaterally (mainly the bilateral anterior semicircular canals). The Brandt-Daroff method induced nausea; therefore that examination method was abandoned. Habitual training advocated by St. Marianna University, the Head shaking method from Yamaguchi University, and the Non-specific training method from Toho University did not improve the nystagmus. Vestibular training by Kitazato University improved her vertiginous feeling. The direction of nystagmus changed variously during the course. The vertiginous feeling had almost disappeared in June 2009, but nystagmus persisted. We considered that cupulolithiasis in the bilateral lateral semicircular canals often shifted to canalolithiasis in various portions of the semicircular canals. Appropriate physical therapy improved the subjective symptoms.
Joubert syndrome is a rare autosomal recessive disorder characterized by a specific congenital malformation of the cerebellar vermis. Diagnostic criteria for it include hypotonia, ataxia, episodic hyperpnoea, psychomotor delay, abnormal eye-movement, and the molar tooth sign on magnetic resonance imaging (MRI). We present a 12-month-old boy with Joubert syndrome referred to our hospital because of vertigo. On equilibrium examination, he exhibited left-beating gaze nystagmus, and right-beating horizontal nystagmus, up-beating nystagmus, and alternating nystagmus with a torsional component on positional nystagmus examination. Saccades were preceded by slow eye movement ending with a glissade, and were followed by postsaccadic drift. His smooth pursuit to the left was saccadic, and optokinetic nystagmus gains were reduced. Three months later, his symptoms gradually resolved, his gaze nystagmus nearly disappeared, and only right-beating nystagmus on positional examination was detected.
Although many patients visit the emergency room (ER) with disequilibrium, the epidemiology of these cases has not been well delineated. In this single institutional study, 650 patients presenting to the ER with a complaint of disequilibrium from April 1, 2008, to March 31, 2009 were analyzed from chart review by classifying the symptom into 3 subtypes; dizziness, vertigo and presyncope. Age, gender, neurological findings, resource uses, diagnosis, and the results of specialist consultation were assessed. Patients with dizziness were associated with greater neurological disorders than vertigo patients (p<0.05). The sensitivity of head CT was as low as 30% for ischemic stroke. About 60% of the diagnoses in ER remained as a symptomatic diagnosis. The total ratio of dangerous disorders was 8.5%. It should always be noted that disequilibrium in ER is often associated with life-threatening disorders.
Binswanger's encephalopathy is a form of vascular dementia characterized by extensive degeneration of the cerebral white matter and multiple lacunar infarcts. Extensive damage to the white matter causes disruption of both the Cortico-cortical and Cortico-subcortical neural networks, resulting in the so-called disconnection syndrome. As white matter lesions are particularly prominent in the frontal lobe, abnormal eye movements may result from impairment of pathways between the frontal eye fields and other cortical eye fields, as well as the basal ganglia, brain stem, and cerebellum. In the present study, we evaluated eye movements in three patients with Binswanger's encephalopathy using electronystagmography. No clear limited range of eye movements or gaze-evoked nystagmus was observed in any of the patients. Mild impairment of pursuit was seen in all patients. As for saccades, all patients had mild hypometria and slow vertical saccades, while two also had slow horizontal saccades. In addition, saccade latency was prolonged horizontally and vertically in two patients. Decrease in the slow phase of optokinetic nystagmus (OKN) was also observed in all patients, but the decrease was significant in only one patient. No impairment of visual suppression (VS) was seen. Few studies have investigated impairment of eye movements in Binswanger's encephalopathy. The present study showed characteristic abnormal eye movements in the patients, relatively mild impairment of pursuit, saccade and OKN, and slow saccades, but no impairment of VS. These findings were different from eye movement abnormalities caused by cerebellar, brain stem lesions or cortical dementia.