Tae-Ho Yang

Topology of brainstem lesions associated with subjective visual vertical tilt

Objective: We aimed to determine the topology of anatomical pathways for verticality perception in the brainstem. Methods: We measured the subjective visual vertical (SVV) in 82 patients with acute unilateral infarction of the brainstem alone. The topology of the brainstem lesions responsible for pathologic SVV tilt were determined using MRI-based voxel-wise lesion-behavior mapping, from which probabilistic lesion maps were constructed. Results: Fifty percent of patients (41/82) with acute unilateral brainstem infarcts had abnormal SVV tilt, of which 76% (31/41) had ipsiversive tilt and 24% (10/41) had contraversive tilt. Patients with contraversive SVV tilt exhibited overlapping lesions of the rostral medial vestibular nucleus, medial longitudinal fasciculus, rostral interstitial medial longitudinal fasciculus, and interstitial nucleus of Cajal. In contrast, patients with ipsiversive SVV tilt and oculomotor disturbances exhibited lesions of the medial and inferior vestibular nuclei in the caudal medulla, while those with isolated vertical perceptual changes had injury to the medial side of the medial lemniscus. Conclusions: Our findings provide evidence of a pathway transmitting ipsiversive otolithic signals that bypass the oculomotor system at the medial side of the medial lemniscus, called the ipsilateral vestibulothalamic tract.

Geotropic central paroxysmal positional nystagmus in a patient with human immunodeficiency virus encephalopathy.

Central vestibular lesions may cause paroxysmal positional nystagmus (PPN) or paroxysmal positional vertigo as a result of lesions involving the brainstem dorsolateral to the fourth ventricle or the cerebellar nodulus/uvular region. PPN usually presents as persistent downbeating nystagmus during head hanging or as apogeotropic horizontal nystagmus during head turning in the supine position. Geotropic PPN during head turning in the supine position has not been previously reported. We report such a case in a patient with HIV encephalopathy.

Persistent otolith dysfunction even after successful repositioning in benign paroxysmal positional vertigo

To evaluate utricular and saccular function during the acute and resolved phases of BPPV, ocular and cervical vestibular evoked myogenic potentials (VEMPs) were studied in 112 patients with BPPV and 50 normal controls in a referral-based University Hospital. Ocular (oVEMPs) and cervical VEMPs (cVEMPs) were induced using air-conducted sound (1000Hz tone burst, 100dB normal hearing level) at the time of initial diagnosis and 2 months after successful repositioning in patients with BPPV, and the results were compared with those of the controls. Abnormalities of cVEMPs and oVEMPs in patients with BPPV were prevalent and significantly higher compare to the healthy control group (p<0.01 in each VEMP by chi-square test). In the patient group, difference between the proportions of abnormal responses of cVEMP and oVEMP was not significant in both affected (p=0.37, chi-squared test) and non-affected (p=1.00) ears. The abnormalities were more likely reduced or absent responses rather than delayed ones; reduced or absent responses are 17.6% in cVEMPs (p=0.04, chi-square) and 21.6% in oVEMPs (p<0.01). The non-affected ear in the BPPV group also showed significantly higher abnormalities of cVEMP and oVEMP when compared to the control group. The follow-up VEMPs after repositioning maneuvers were not significantly different compared to the initial values from both stimulated affected and non-affected ears. Although most patients had unilateral BPPV, bilateral otolithic dysfunction was often shown by persistently reduced or absent cervical and ocular VEMPs, suggesting that BPPV may be caused by significant bilateral damage to the otolith organs.

Recurrent Streptococcus Pneumoniae Meningoencephalitis in a Patient With a Transethmoidal eningoencephalocele

We report a case of recurrent Streptococcus Pneumoniae meningoencephalitis with a transethmoidal meningoencephalocele (TEME) but without cerebrospinal fluid (CSF) leakage. A 35-year-old man was admitted with S. pneumoniae meningitis. He had suffered from four episodes of recurrent pneumococcal meningitis during the previous 4 years. A computed tomography scan of the paranasal sinus showed the TEME protruding through a bony defect of the right frontal base. However, the patient did not have symptoms that could be attributable to CSF leakage, and radioisotope cisternography did not identify a leak. Brain magnetic resonance imaging revealed cortical lesions overlying the TEME, and electroencephalography revealed epileptiform discharges in frontal regions. Appropriate antibiotics therapy without steroids was given to improve his condition. The presented case suggests that even in the absence of clinically demonstrable CSF leakage, an occult skullbase defect and its associated meningoencephalocele should be considered in patients with recurrent bacterial meningitis.

Clinical classification and neuro-vestibular evaluation in chronic dizziness

OBJECTIVE This study attempts to clarify the clinical characteristics of chronic dizziness and its relationships with specific vestibular, oculomotor, autonomic and psychiatric dysfunctions. METHODS 73 Patients with idiopathic chronic dizziness were recruited and classified based on history taking and clinical examination into the following four clinical subgroups; vestibular migraine (VM), dysautonomia, psychogenic, and unspecified groups. They were also evaluated using oculomotor, otolithic and autonomic function tests, and psychologic investigation. RESULTS Patients in the VM group showed a high proportion of abnormality on smooth pursuit and otolithic function testing compared to the other groups. The dysautonomia group revealed significant abnormalities in sympathetic and cardiovagal autonomic function, while the psychogenic group had a high frequency of abnormality in sympathetic autonomic testing and in Becks anxiety inventory scale. The unspecified group showed abnormalities on saccade, smooth pursuit and autonomic function testing. CONCLUSIONS Clinical classification of patients with chronic dizziness was relevant and they showed a correlation with disease-specific abnormal results in oculomotor, otolithic, autonomic function and psychology testing. SIGNIFICANCE Appropriate diagnostic investigation based on precise clinical diagnosis of chronic dizziness reduces the need for extensive laboratory testing, neuroimaging, and other low-yield tests.

Homonymous Visual Field Loss without Structural Lesion on Magnetic Resonance Imaging: Documented with Positron Emission Tomography and Diffusion Tensor Imaging

Abstract The authors describe a 35-year-old man suffering from homonymous hemianopia after head trauma 4 years before but with negative magnetic resonance imaging (MRI) findings. Brain fluorine-18 fluorodeoxyglucose positron emission tomography (18FDG-PET) showed hypometabolism at the unilateral occipital lobe and crossed cerebellar hemisphere, and diffusion tensor imaging (DTI) revealed that the ipsilateral optic radiations were completely interrupted. The crossed cerebellar diaschisis (CCD) observed in the chronic stage of brain damage was caused by cerebellar suppression of the cerebral blood flow due to an involvement of the corticopontocerebellar tract. PET and DTI provide objective means for determining the relationship of functional deficits to head trauma, even in cases where the injury was sustained years prior to the evaluation.

Intermittent Theta Slowings in Contralateral Side of Weakness after Sleep Deprivation on Spot EEG in Sporadic Hemiplegic Migraine

Hemiplegic migraine (HM) is an uncommon type of migraine which is classified into sporadic and familial subtype. The noticed electroencephalogram (EEG) findings during HM attack are diffuse slowing contralateral to the weakened limb, but are usually normal in asymptomatic states. A 52-year-old woman who suffered from headache accompanying right arm weakness and aphasic symptoms admitted to our hospital. She underwent total five times of EEG including 2 times before admission. Only the last EEG exam after 24 hours of sleep deprivation (SD) showed intermittent slowing and higher amplitude of positive occipital sharp transients (POSTs) on the left parieto-occipital area. Here, we report a case with HM who revealed abnormal EEG findings after SD, which was not observed in the routine EEG study without SD.

Air- and bone-conducted cervical and ocular vestibular-evoked myogenic potentials in patients with superior vestibular neuritis

OBJECTIVE: To determine the characteristic changes in cervical (cVEMP) and ocular (oVEMP) vestibular evoked myogenic potentials to different stimuli by using air-conducted sound (ACS) and bone-conducted vibration (BCV) in patients with superior vestibular neuritis (SVN). BACKGROUND: There has been debate about the origin of the VEMP, especially the ocular VEMP (oVEMP) activated by ACS and BCV at different sites. DESIGN/METHODS: Using ACS and BCV stimuli, cVEMPs and oVEMPs were recorded in SVN patients (n=33) and normal controls (n = 45). RESULTS: ACS induced cVEMPs revealed mostly normal (81.9%) whereas results of ACS induced oVEMPs showed high rates of abnormalities (82%). oVEMP by BCV at the mid-frontal (Fz) revealed high rates of abnormalities (62.5%) especially on the contralesional eye and none of them showed abnormality on the ipsilesional eye. cVEMPs and oVEMPs induced by BCV at the mastoid process revealed dissociated results. cVEMP to mastoid BCV showed low rates of abnormalities (31.2%) whereas oVEMP to mastoid BCV revealed high rates of abnormalities (75%). CONCLUSIONS: The oVEMP in response to ACS may be mediated by the superior vestibular nerve, probably due to an activation of the utricular receptors. The high rates of abnormalities in Fz BCV oVEMP also suggest a dependence on the intactness of the superior vestibular nerve afferents. The dissociations in the abnormalities of cVEMP and oVEMP induced by BCV at the mastoid in patients with VN selectively involving the superior vestibular nerve suggest that the origin of the vestibular nerve afferents of oVEMP to mastoid BCV differ from those of cVEMP to mastoid BCV. Therefore oVEMP to mastoid BCV also reflects functions of the superior vestibular nerve afferents and most likely the utricular function. Disclosure: Dr. Oh has nothing to disclose. Dr. Kim has nothing to disclose. Dr. Shin has nothing to disclose. Dr. Yang has nothing to disclose. Dr. Jeong has nothing to disclose.