Medial Longitudinal Fasciculus Research Articles

Pearls & Oy-sters: INO Plus From Downward Herniation-A Cautionary Tale Regarding Neuro-Ophthalmologic Signatures of Brainstem Compression.

Pupillary assessment is a quintessential part of the clinical examination in neuro-intensive care patients because it provides insight into the integrity of midbrain reflex arcs. Abnormal pupils, particularly anisocoria and later bilateral fixed mydriasis, are classically used to assess expansive intracranial processes because they are frequently considered early indicators of transtentorial midbrain compression due to elevated intracranial pressure. Complex ocular motor deficits mapping to the midbrain are rarely described in the setting of high transtentorial pressure. This is likely because ocular motor deficits typically occur in conjunction with decreased consciousness and corticospinal tract dysfunction reflecting advanced midbrain compromise. We present a case of left midbrain compression due to downward herniation in a patient with acute-on-chronic bilateral subdural hematoma. Ocular motor assessment demonstrated left internuclear ophthalmoplegia (INO) and an ocular tilt reaction, termed INO plus. However, pupillary, mental status, and sensorimotor examinations were unremarkable. Head magnetic resonance imaging revealed acute perforator ischemia in the left pontomesencephalic tegmentum, localizing to the ipsilateral medial longitudinal fasciculus and graviceptive oculocephalic circuits. Microvascular compromise secondary to mechanical pressure is discussed as a causative mechanism. We caution against overreliance on "telltale pupils" in suspected brainstem compression and recommend checking for other oculomotor signs.

Pure downgaze palsy from isolated infarction of the left paramedian thalamic-mesencephalon junction.

A 65-years-old female was hospitalized 24 h after experiencing the sudden onset of subjective reduction in visual acuity and hypersomnia. On admission to the neurological ward, she presented isolated downgaze palsy. A Magnetic Resonance Imaging of the brain disclosed a discrete, ovalar hyperintensity involving the left paramedian thalamic-mesencephalon junction. The lesion was consistent with infarction. Isolated downgaze palsy has been described in thrombosis of Artery of Percheron leading to infarction of bilateral paramedian thalami along with structures from the mesencephalic-diencephalic junction such as the Medial Longitudinal Fasciculus (riMLF). While neurons from the riMLF controlling upward vertical saccades project to either ipsilateral and contralateral oculomotor nuclear complexes, those involved in regulating downgaze descend ipsilaterally in the brain stem. Isolated downgaze palsy has an extreme localizer value to the diencephalic-mesencephalon junction and can arise from a unilateral lesion.

Bilateral hypogeusia and food aversion due to lacunar infarct in the right dorsomedial pontine tegmentum.

A 70-year-old right-handed housewife suffered an acute loss of taste, an unpleasant change in the taste of foods and liquids, and a strong aversion to all kinds of food due to a small lacune in the right dorsomedial pontine tegmentum. Eating became so unpleasant that she lost 7 kg in three weeks. Olfaction and the sensibility of the tongue were spared. The right medial longitudinal fascicle, the central tegmental tract, or both, were injured by the tegmental lesion. A discrete right-sided lesion in the upper pontine tegmentum may cause a reversible syndrome consisting of bilateral hypogeusia which is more severe ipsilaterally.

Unilateral Internuclear Ophthalmoplegia in a 14-year-old Female

Purpose: Internuclear ophthalmoplegia (INO) is an eye movement disorder caused by a lesion of the medial longitudinal fasciculus. It typically manifests bilaterally and is commonly caused by multiple sclerosis. We report a case of pediatric unilateral INO, which is rare in the pediatric population.Case summary: A 14-year-old female, with a history of traumatic head injury 9 days previously, presented with diplopia, nausea and vomiting for the past 5 days. Her ophthalmic examination revealed severely impaired adduction of the right eye and abduction nystagmus in the left eye. Orbital computed tomography showed no evidence of orbital wall fracture or muscle impingement. However, an magnetic resonance imaging of her brain demonstrated an infarct in the right paramedian midbrain, leading to a diagnosis of unilateral INO. Diplopia and impaired adduction of the right eye resolved completely 7 weeks after the trauma.Conclusions: Demyelinating diseases, such as multiple sclerosis, account for most of the pediatric INO cases. Although most of these cases are bilateral, this reports highlights a pediatric case of unilateral INO following head injury, which is an uncommon occurrence in this age group.

Progressive Bilateral Ptosis in Adduction Deficit: True Internuclear Ophthalmoplegia (INO) or Pseudo-INO?

Abstract
 Introduction : Bilateral INO is a rare disease caused by a lesion in the medial longitudinal fasciculus (MLF) in the pons, resulting in adduction deficit. Progression to ptosis is rare and may confuse with pseudo-INO as in ocular myasthenia gravis (OMG). This case aims to report progressive ptosis in bilateral INO that mimics pseudo-INO.
 Case Illustration : A 36-year-old woman complained sudden binocular diplopia 4 days before admission. Bilateral adduction deficits (-3 and -2 of right and left eye, respectively) with nystagmus were seen. There was no ptosis. The patient was diagnosed with bilateral INO. One month later, the patient returned with bilateral ptosis. The marginal reflex distance 1 (MRD1) were 0 on both eyes. Post fatigue and ice pack test showed 2mm difference of MRD1. The single fiber electromyography (EMG) result came out negative with jitter <10%. Brain MRI revealed lesions in the posterior pons and periaqueductal on the level of midbrain.
 Discussion : The MLF controls 6th and contralateral 3rd cranial nerve nucleus for horizontal gaze. Ptosis in INO can occurred due to central caudal subnucleus involvement in midbrain that innervates levator palpebra. The result of fatigue and ice pack test may be misleading, as those are not pathognomonic for OMG. The single-fiber EMG are valuable modalities to exclude pseudo-INO in this case.
 Conclusion : Progressive bilateral ptosis may occur in bilateral INO. Fatigue and ice pack test may give false- positive results leading to confusion with pseudo-INO, rather than true INO. Supporting examinations are needed to confirm the diagnosis.

Internuclear ophthalmoplegia as a presentation of procedural stroke: a case report

BackgroundCardiac catheterization and endovascular procedures are extensively used in modern medicine, and procedural stroke is one of the major complications that the catheterization laboratory team may face in their everyday work. Recognizing the signs and symptoms of procedural stroke is crucial to ensuring appropriate management. We herein report a case of internuclear ophthalmoplegia that caused blurred vision, diplopia, and dizziness on lateral gaze as an unusual presentation of procedural stroke.Case presentationA 60-year-old Thai woman underwent right partial colectomy and was diagnosed with stage IV diffuse large B-cell lymphoma. Pre-chemotherapy echocardiography revealed mild left ventricular systolic dysfunction, and she therefore underwent diagnostic catheterization. Coronary angiography revealed normal coronary arteries, leading to a diagnosis of non-ischemic cardiomyopathy. After the procedure, she immediately developed dizziness and diplopia. During the right lateral gaze, she exhibited impaired adduction of the left eye and horizontal nystagmus of the right eye. A diagnosis of left internuclear ophthalmoplegia was made. Magnetic resonance imaging revealed a tiny area exhibiting characteristics of an acute infarct in the left paramedian midbrain, including the left medial longitudinal fasciculus, which explained the clinical picture. Another region of restricted diffusion indicating an acute infarct was detected in the right inferior cerebellar hemisphere. Magnetic resonance angiography revealed no significant cerebral artery disease. The patient achieved full neurological recovery 6 weeks after symptom onset.ConclusionThis report describes an uncommon presentation of procedural stroke that is likely to be misdiagnosed, especially by medical staff unfamiliar with internuclear ophthalmoplegia. Despite the good prognosis of internuclear ophthalmoplegia, appropriate stroke care is crucial in patients with procedural stroke because of the risk of multiple brain infarcts.

Genoarchitectonics of the larval zebrafish diencephalon.

The brain is spatially organized into subdivisions, nuclei and areas, which often correspond to functional and developmental units. A segmentation of brain regions in the form of a consensus atlas facilitates mechanistic studies and is a prerequisite for sharing information among neuroanatomists. Gene expression patterns objectively delineate boundaries between brain regions and provide information about their developmental and evolutionary histories. To generate a detailed molecular map of the larval zebrafish diencephalon, we took advantage of the Max Planck Zebrafish Brain (mapzebrain) atlas, which aligns hundreds of transcript and transgene expression patterns in a shared coordinate system. Inspection and co-visualization of close to 50 marker genes have allowed us to resolve the tripartite prosomeric scaffold of the diencephalon at unprecedented resolution. This approach clarified the genoarchitectonic partitioning of the alar diencephalon into pretectum (alar part of prosomere P1), thalamus (alar part of prosomere P2, with habenula and pineal complex), and prethalamus (alar part of prosomere P3). We further identified the region of the nucleus of the medial longitudinal fasciculus, as well as the posterior and anterior parts of the posterior tuberculum, as molecularly distinct basal parts of prosomeres 1, 2, and 3, respectively. Some of the markers examined allowed us to locate glutamatergic, GABAergic, dopaminergic, serotoninergic, and various neuropeptidergic domains in the larval zebrafish diencephalon. Our molecular neuroanatomical approach has thus (1) yielded an objective and internally consistent interpretation of the prosomere boundaries within the zebrafish forebrain; has (2) produced a list of markers, which in sparse combinations label the subdivisions of the diencephalon; and is (3) setting the stage for further functional and developmental studies in this vertebrate brain.

Brainstem anatomy with 7-T MRI: in vivo assessment and ex vivo comparison

Background The brainstem contains grey matter nuclei and white matter tracts to be identified in clinical practice. The small size and the low contrast among them make their in vivo visualisation challenging using conventional magnetic resonance imaging (MRI) sequences at high magnetic field strengths. Combining higher spatial resolution, signal- and contrast-to-noise ratio and sensitivity to magnetic susceptibility (χ), susceptibility-weighted 7-T imaging could improve the assessment of brainstem anatomy.MethodsWe acquired high-resolution 7-T MRI of the brainstem in a 46-year-old female healthy volunteer (using a three-dimensional multi-echo gradient-recalled-echo sequence; spatial resolution 0.3 × 0.3 × 1.2 mm3) and in a brainstem sample from a 48-year-old female body donor that was sectioned and stained. Images were visually assessed; nuclei and tracts were labelled and named according to the official nomenclature.ResultsThis in vivo imaging revealed structures usually evaluated through light microscopy, such as the accessory olivary nuclei, oculomotor nucleus and the medial longitudinal fasciculus. Some fibre tracts, such as the medial lemniscus, were visible for most of their course. Overall, in in vivo acquisitions, χ and frequency maps performed better than T2*-weighted imaging and allowed for the evaluation of a greater number of anatomical structures. All the structures identified in vivo were confirmed by the ex vivo imaging and histology.ConclusionsThe use of multi-echo GRE sequences at 7 T allowed the visualisation of brainstem structures that are not visible in detail at conventional magnetic field and opens new perspectives in the diagnostic and therapeutical approach to brain disorders.Relevance statementIn vivo MR imaging at UHF provides detailed anatomy of CNS substructures comparable to that obtained with histology. Anatomical details are fundamentals for diagnostic purposes but also to plan a direct targeting for a minimally invasive brain stimulation or ablation.Key points• The in vivo brainstem anatomy was explored with ultrahigh field MRI (7 T).• In vivo T2*-weighted magnitude, χ, and frequency images revealed many brainstem structures.• Ex vivo imaging and histology confirmed all the structures identified in vivo.• χ and frequency imaging revealed more brainstem structures than magnitude imaging.Graphical

Clinical Insights into Internuclear Ophthalmoplegia: A Case Report

Background: Internuclear ophthalmoplegia (INO) is a rare neuro-ophthalmological disorder characterized by impaired horizontal eye movement coordination due to lesion in the medial longitudinal fasciculus. INO commonly results from demyelinating diseases, vascular lesions, or structural brain abnormalities.
 Case presentation: A 60-year-old male patient presented with diplopia for the past 4 days. He had history of hypertension and diabetes mellitus and “mild” stroke for past years. Clinical examination revealed normal primary gaze, limited medial movement of the left eye, and diplopia in all gaze positions. Hess screen examination demonstrated underaction of the left medial rectus muscle and overaction of the right lateral rectus muscle. The laboratory results an elevated blood sugar level. Brain CT scan revealed multiple infarcts in the right parietal and cerebellar lobes and left parieto-occipital lobe, with evidence of brain atrophy. The patient was diagnosed with INO. Management involved addressing the underlying systemic diseases, namely diabetes and hypertension, in collaboration with internist and neurologist. The patient also received citicoline therapy and underwent regular follow-up. In the third-month follow-up, the patient demonstrated significant improvement, with reduction in diplopia and enhancement in left eye medial movement.
 Conclusion: This case report highlights the importance of considering INO in patients presenting with diplopia and a history of vascular risk factors. Timely diagnosis and comprehensive management with regular follow-up is crucial to monitor the progress and enhance the patient's quality of life.

Abstract 102: Pseudo‐Internuclear Ophthalmoplegia in a Patient with an Acute Globus Pallidus Infarct: A Case Report

Introduction Internuclear ophthalmoplegia (INO) is an ocular movement disorder typically due to a lesion in the medial longitudinal fasciculus (MLF). Rarely, similar ocular movement abnormalities can be observed in the absence of an MLF lesion. This case report aims to highlight a potential association between acute globus pallidus (GP) infarct and an ocular movement abnormality resembling INO. Methods N/A Results Case Presentation: A 72‐year‐old male with a medical history significant for chronic myeloid leukemia, prostate cancer, type 2 diabetes mellitus, hypertension, prior stroke, and heart failure presented with dizziness. Examination revealed right INO, skew deviation with right hypertropia, left lower extremity weakness, left upper extremity dysmetria, right facial weakness (prior deficit), and ataxic gait. MRI of brain confirmed an acute lacunar infarct in the right globus pallidus with no apparent brainstem or cerebellar lesion. The patient was started on dual antiplatelet therapy and discharged with home rehabilitation services to improve his balance. Discussion: The patient presented with pseudo‐INO in the setting of an acute globus pallidus infarct. This case introduces the idea that ocular motor abnormalities resembling INO could occur due to a GP lesion, which was not previously reported. The basal ganglia control saccadic eye movements by means of their connection to the superior colliculus (SC). GP was shown to have a role in this connection which may provide a plausible explanation for this observation. Another possible explanation can be based on the concept of diaschisis, where a lesion in a specific area of the brain (GP in this case) can lead to deficits or impairments in various functions associated with that region (the SC and its pathway for controlling saccadic eye movement). Conclusion This case emphasizes that slow adducting saccades and associated nystagmus is not always INO.

A rare case report: isolated midbrain lacunar infarct affecting the ipsilateral medial longitudinal fasciculus causing internuclear ophthalmoplegia effect

Isolated medial longitudinal fasciculus infarct is rare and can also be associated with cranial nerve nuclei or extra-nuclear regions leading to respective neurological deficit. We report a case of 73-year-old woman presenting with a 24 hour of confusion, abnormal eye movement and unsteady gait on a background history of uncontrolled diabetes mellitus (DM), hypertension and Alzheimer’s disease. Her examination found to have dysdiadokinesia in left upper limb and inability to adduct right eyeball on left lateral gaze, without affecting the pupil. She was not oriented to time and place while before this event she could. Her examination found to have normal power in limbs and sensation. Her computed tomography (CT) brain showed no evidence of acute infarction or intracranial bleed. Magnetic resonance imaging (MRI) brain demonstrated acute lacunar infarct involving the ipsilateral medial longitudinal fasciculus. This case demonstrates rare brainstem infarct affecting medial longitudinal fasciculus region below the IIIrd cranial nerve nucleus giving features of internuclear ophthalmoplegia affecting medial rectus muscle without affecting autonomic fibres of IIIrd cranial nerve due to which the pupil is not affected. We recommend strict control of predisposing conditions, mainly diabetes and hypertension to reduce the incidence of brainstem stroke.

The mesencephalic locomotor region recruits V2a reticulospinal neurons to drive forward locomotion in larval zebrafish

The mesencephalic locomotor region (MLR) is a brain stem area whose stimulation triggers graded forward locomotion. How MLR neurons recruit downstream vsx2+ (V2a) reticulospinal neurons (RSNs) is poorly understood. Here, to overcome this challenge, we uncovered the locus of MLR in transparent larval zebrafish and show that the MLR locus is distinct from the nucleus of the medial longitudinal fasciculus. MLR stimulations reliably elicit forward locomotion of controlled duration and frequency. MLR neurons recruit V2a RSNs via projections onto somata in pontine and retropontine areas, and onto dendrites in the medulla. High-speed volumetric imaging of neuronal activity reveals that strongly MLR-coupled RSNs are active for steering or forward swimming, whereas weakly MLR-coupled medullary RSNs encode the duration and frequency of the forward component. Our study demonstrates how MLR neurons recruit specific V2a RSNs to control the kinematics of forward locomotion and suggests conservation of the motor functions of V2a RSNs across vertebrates.

From WEMINO To WEBINO With Unilateral LMN Facial Palsy (P5-4.002)

<h3>Objective:</h3> To describe a case of progression from apparent trochlear nerve palsy, to wall-eyed monocular internuclear ophthalmoplegia (WEMINO), to wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) with unilateral lower motor neuron (LMN) facial palsy. <h3>Background:</h3> Various descriptions of INO with cranial nerve palsies are in the literature, but we report a patient with a remarkably instructive stepwise evolution. <h3>Design/Methods:</h3> Review of records of a patient with diplopia at our institution. <h3>Results:</h3> A 42-year-old woman presented acutely with oblique binocular diplopia worsening on right gaze and left head tilt, with left hypertropia. Trochlear nerve palsy was suspected but contrasted MRI brain with orbits, and initial CSF testing were unrevealing. On day 3, the hypertropia partly improved but she developed left eye adduction deficit. Given the fluctuation, myasthenia gravis was considered high in the differential diagnosis while test results were awaited. On day 7, she developed LMN left facial palsy and bilateral adduction deficit with abducting eye nystagmus, leading to the realization that a single progressing lesion in the pontine tegmentum could explain her entire sequence of events. Repeat MRI confirmed a minute enhancing lesion in the floor of the fourth ventricle corresponding to the dorsomedial surface of the left facial colliculus and bilateral medial longitudinal fasciculi (MLF), likely of demyelinating etiology. Her pending CSF tests returned with 7 oligoclonal bands. She received intravenous methylprednisolone and her symptoms nearly resolved by day 14. <h3>Conclusions:</h3> This patient presented with evolving symptoms that appeared to localize to the trochlear nerve initially, but lacked imaging correlate. It is clear in retrospect that her initial presentation represented a skew deviation from early INO, progressing to WEMINO and eventually WEBINO with unilateral fascicular facial palsy. The anatomical correlate was confirmed on repeated imaging. Her clinical course beautifully illustrates the importance of lesion localization for etiological diagnosis. <b>Disclosure:</b> Dr. Senthamarai Siddharthan has nothing to disclose. Dr. Witt has nothing to disclose. Dr. Kini has nothing to disclose. Dr. Vasireddy has nothing to disclose. The institution of Dr. Mathur Kumaraswamy has received research support from Woolsey Pharmaceuticals.

Teaching Video NeuroImages: Pulsatile proptosis and wall-eyed bilateral internuclear ophthalmoplegia

A 65-year-old man with a history of hypertension presented with double vision. Examination revealed wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) (figure 1) and nonsymptomatic, pulse-synchronous, pulsatile proptosis of the left eye (video 1). According to the patient, there was a history of blunt head trauma in childhood and the pulsatile eye was present since then. CT revealed a meningocele into the left orbit due to a bony defect in the orbital roof (figure 2A). CT angiography ruled out a carotid-cavernous fistula. MRI showed an acute infarction at the midline of the midbrain tegmentum, which involved the medial longitudinal fasciculus bilaterally and caused the WEBINO (figure 2B).1 The pulsatile proptosis was attributed to the childhood head injury and due to the orbital roof fracture and associated meningocele pulsation of the brain vessels passed onto the CSF.2

Cavernous Malformations: What They Have Taught Us.

Cavernous Malformations: What They Have Taught Us.

Biomechanics and neural circuits for vestibular-induced fine postural control in larval zebrafish

Land-walking vertebrates maintain a desirable posture by finely controlling muscles. It is unclear whether fish also finely control posture in the water. Here, we showed that larval zebrafish have fine posture control. When roll-tilted, fish recovered their upright posture using a reflex behavior, which was a slight body bend near the swim bladder. The vestibular-induced body bend produces a misalignment between gravity and buoyancy, generating a moment of force that recovers the upright posture. We identified the neural circuits for the reflex, including the vestibular nucleus (tangential nucleus) through reticulospinal neurons (neurons in the nucleus of the medial longitudinal fasciculus) to the spinal cord, and finally to the posterior hypaxial muscles, a special class of muscles near the swim bladder. These results suggest that fish maintain a dorsal-up posture by frequently performing the body bend reflex and demonstrate that the reticulospinal pathway plays a critical role in fine postural control.

Abstract Number ‐ 226: Pontine Stroke Presenting as 1.5 Syndrome Evolving to 9 Syndrome over 72 Hours.

Introduction A 75 year old woman with a past medical history of hypertension developed sudden‐onset vertigo, nausea and vomiting. She did not immediately seek medical care, thinking she was suffering from food poisoning. The following day her symptoms improved however she developed new right sided weakness and gait imbalance, prompting her presentation to the ED. Her neurologic exam noted complete loss of adduction of the right eye and loss of horizontal extraocular movements of the left eye. She also displayed right upper extremity paresis, right upper extremity dysmetria and mild dysarthria. MRI of the brain disclosed acute pontine infarcts in the ventral and dorsal left paramedian regions. Over the next three days, her horizontal gaze palsy improved with some return of adduction of the right eye and horizontal movements of the left eye. However right sided paresis worsened, and in addition, progressed to include complete left facial palsy (lower motor neuron lesion). She was able to be discharged to rehab, placed on Aspirin 81 mg daily and Ezetimibe (due to elevated liver function enzymes) and 30 day Cardiac Event Monitor follow up. Methods Case report and review of literature. Results Due to the combination of multiple cranial nuclei and white matter tracts in the brainstem, ischemia can lead to several clinical manifestations. There are various presenting clinical syndromes, named numerically by structures involved and/or the clinical deficit. One‐and‐a‐half (1.5) syndrome, first reported by Fischer in 1967, is an uncommon entity caused by a lesion (most commonly infarction) in the pontine tegmentum [1]. It consists of complete ipsilateral horizontal gaze palsy (due to involvement of ipsilateral Paramedian Pontine Reticular Formation/Abducens Nucleus and Medial Longitudinal Fasciculus) and loss of adduction of the contralateral eye (due to involvement of the contralateral Medial Longitudinal Fasciculus). Extension of the lesion to the facial nucleus can produce ipsilateral lower motor neuron type facial palsy, leading to an even more uncommon 8.5 syndrome (7 + 1.5), described by Eggenberger in 1998 [2]. When the lesion involves the corticospinal tracts and/or the medial lemniscus, it can lead to contralateral hemiparesis and/or hemisensory deficits; the so called “9 syndrome” first proposed by Rosini et al in 2013 [3]. This rare entity has been reported in only a handful of cases. Conclusions The awareness of complex brainstem neuroanatomy enables precise localization of the clinical deficits. The noted slow progression of the clinical syndrome from 1.5 to 8.5 and finally 9 syndrome over 72 hours in this case highlights the complexity of small vessel brainstem ischemia.

Pons Lezyonlarının İki Nadir Prezentasyonu: Bir Buçuk Ve Sekiz Buçuk Sendromu

One-and-a-half syndrome refers to a unilateral lesion involving the ipsilateral medial longitudinal fascicle and the 6th cranial nevre nucleus and/or the paramedian pontine reticular formation. Eight-and-a-half syndrome is a syndrome in which one-and-a-half syndrome and ipsilateral 7th cranial nevre palsy are seen together. These rare conditions result from limited lesions of the pontine tegmentum. We presented two cases with one-and-a-half and eight-and-a-half syndromes with ischemic infarction and hemorrhage in pons, respectively.

Loss of torsional quick eye movements during head roll in progressive supranuclear palsy: anew diagnostic marker.

Even though impaired horizontal and vertical saccades are well-known features of progressive supranuclear palsy (PSP), abnormalities of torsional quick phases of eye movements have not been defined in PSP and other Parkinsonian syndromes. This study aims to determine the diagnostic value of decreased torsional quick phases during head oscillations in the roll plane in patients with PSP. Using video-oculography, we recorded the head and eye motion during passive head oscillations in the roll plane and determined the decrease of torsional quick phases in patients with PSP (n = 13) in comparison to normal controls (n = 13) and those with multiple system atrophy (MSA, n = 17)or idiopathic Parkinson's disease (PD, n = 6). Torsional quick phases were absent during the torsional vestibulo-ocular reflex (VOR) in 78.6% (11/13) of the patients with PSP, but only in 11.8% (2/17) of those with MSA and none with idiopathic PD or of normal controls (Chi-square tests, p < 0.001) while gains of the torsional VOR did not differ among the groups (Chi-square tests, p > 0.05). Furthermore, the torsional quick phases were smaller even when observed in patients with PSP. Loss of torsional quick phases is an early biological marker for diagnosis of PSP, and may be ascribed to degeneration of the rostral interstitial nucleus of the medial longitudinal fasciculus that contains the burst neurons for torsional as well as vertical saccades.

Sensitivity of Magnetic Resonance Imaging of the Medial Longitudinal Fasciculus in Internuclear Ophthalmoplegia.

Internuclear ophthalmoplegia (INO) is a result of insult to the medial longitudinal fasciculus (MLF). Clinicoradiological correlation in patients with INO has been reported to be poor; however, prior studies have used low resolution MRI imaging techniques and included patients with subclinical INO. We aimed to determine the sensitivity of modern MRI interpreted by a specialist neuroradiologist to detect clinically evident INO. A retrospective chart review of patients in 2 tertiary University-affiliated neuro-ophthalmology practices with the diagnosis of INO. MRI scans of all patients were reviewed and interpreted by a fellowship-trained neuroradiologist for the presence of lesion in MLF and concordance with the original imaging report. Forty-five patients were included in the study: 33 with demyelinating disease, 11 with stroke, and 1 with intracranial mass. A visible MLF lesion was present in 25/33 demyelinating cases and 7/11 ischemic cases. Lesions in 2 cases in each group were identified only after review by a fellowship-trained neuroradiologist. In demyelinating INO, patients with a visible MLF lesion were more likely to show other brainstem (72%) and supratentorial (51%) white matter lesions. In 25% of patients with demyelinating INO and 33% of patients with ischemic INO, no visible lesion was identified on current high-quality MRI imaging. Review of imaging by a neuroradiologist increased the possibility of lesion been identified.