Midbrain Lesions Research Articles

Trans-lamina terminalis suprategmental approach for ventral midbrain lesions: Technical note

Surgical resection of lesions located in the ventral midbrain is challenging. Few approaches and safe entry zones (SEZs) have been proposed and used to remove this type of lesion, and each has its limitations. Using two illustrating cases, the authors describe a trans-lamina terminalis suprategmental approach for removing ventral midbrain lesions. This approach provides a straight surgical trajectory with sparse neurovascular structures and can be performed with a standard pterional or subfrontal craniotomy. It may be the ideal approach for ventromedial midbrain lesions extending towards the third ventricle.

Anti-Ma2-associated encephalitis

A 30 year old male with no relevant previous medical history, consulted in the Emergency Room with a 1-month history of a sleep disorder with daily somnolence, adding 3 days before consultation temporal and spatial disorientation. Family members also referred hyperphagia. The patient didn’t present headache, fever, behavioral manifestations, or any other systemic or neurological signs or symptoms. He denied recent trips or vaccination. 
 Neurological examination was normal. 
 A contrast enhanced brain MRI was performed, revealing in T2/FLAIR weighted images a diffuse hyperintense hypothalamic and interpeduncular lesion with homogeneous contrast enhancement. General laboratory tests were normal, with negative HIV and VDRL results and normal B12 and thyroid function values. A lumbar puncture was performed, showing mononuclear pleocytosis and high protein levels, with a negative citologic test. Full body CT scan showed no alterations, and testicular ecography revealed hypoechoic lesions and macrocalcifications suggestive of testicular cancer. 
 Testicular exeresis was performed, with anatomy pathology findings of seminoma. Paraneoplastic and autoimmune antibodies in CSF showed positive results for anti-Ma2 antibodies. 
 It was concluded that the patient had an Anti-Ma2-associated encephalitis. 
 Chemotherapy was started and the patient received five pulses of methylprednisolone 1g, maintaining long term treatment with high doses of prednisone. The patient had subtle clinical improvement.
 3 months later, the patient consulted in the emergency room for anterograde amnesia. A new brain MRI was done, showing improvement of the hypothalamic lesion but with bilateral hippocampal hyperintensity without contrast enhancement. It was interpreted that the patient had now added an anti-Ma2-associated limbic encephalitis. A new full body CT scan was done, showing new retroperitoneal adenopathies despite chemotherapy. The patient received immunoglobulin 2g/kg and started a new oncologic treatment, with modest clinical improvement in the following months. 
 A new brain MRI was performed a year later, showing only slight hyperintensity in the right wall of the third ventricle in T2/FLAIR sequences and no contrast enhancement.
 Anti-Ma2 antibodies are usually present in men with testicular tumours, and they may be accompanied by a paraneoplastic syndrome including limbic, diencephalic or brainstem encephalitis. Brain MRI shows hyperintensity in the midbrain, diencephalon (thalamus/hypothalamus) or temporal lobes in T2/FLAIR weighted images, with almost half of these lesions presenting with contrast enhancement. CSF regularly has inflammatory changes. 
 Clinical presentation usually varies according to the region affected, and these patients tend to have a good response to oncologic and immunologic treatment, with stabilization or even clinical improvement . 
 Even though this is a rare entity, it is important to consider it as a differential diagnosis in cases of young men with midbrain or diencephalic lesions, since its early diagnosis and treatment could hinder its progression.

Brainstem lesions are associated with sleep apnea in multiple sclerosis.

BackgroundStudies linking MRI findings in MS patients with obstructive sleep apnea severity are limited.ObjectiveWe conducted a retrospective study to assess MRI abnormalities associated with obstructive sleep apnea (OSA) in patients with multiple sclerosis (MS).MethodsWe performed retrospective chart review of 65 patients with multiple sclerosis who had undergone polysomnography (PSG) for fatigue as well as brain MRI. We measured the number of lesions in the brainstem and calculated the standardized third ventricular width (sTVW) as a measure of brain atrophy, and subsequently performed correlation analyses of the apnea-hypopnea index (AHI) with brainstem lesion location, sTVW, and Expanded Disability Status Scale (EDSS).ResultsMS Patients with OSA were significantly older and had a higher body mass index (BMI) and higher AHI measures than patients without OSA. After adjustment for covariates, significant associations were found between AHI and lesion burden in the midbrain (p < 0.01) and pons (p = 0.05), but not medulla.ConclusionsMidbrain and pontine lesions burden correlated with AHI, suggesting MS lesion location could contribute to development of OSA.

Post-Traumatic Weber’s Syndrome: a Rare Presentation

Weber’s syndrome is a midbrain lesion characterized by ipsilateral oculomotor nerve palsy with contralateral hemiparesis or hemiplegia, commonly due to vascular infarct involving paramedian branches of posterior cerebral artery or basilar bifurcation perforating branches. In this case report, we have discussed about a young man who presented with penetrating injury by valve of tyre tube to the right nostril following which he had right side epistaxis with ipsilateral ophthalmoplegia and ptosis with contralateral hemiparesis. Computed tomography evaluation showed presence of sphenoidal bony fragment impinging the midbrain. Patient was managed conservatively. To our best knowledge, traumatic Weber’s syndrome is very rare.

Paroxysmal dysarthria-ataxia syndrome: Literature review on MRI findings and report of a peculiar case with clinically isolated syndrome coexisting with anti-N-methyl-d-aspartate receptor antibodies

Paroxysmal dysarthria and ataxia (PDA) syndrome constitutes a rare neurological disorder, and is generally reported in cases of multiple sclerosis (MS) involving the midbrain. We present an illustrative case of 32-year-old female who developed clinically isolated syndrome manifested paroxysmal dysarthria, ataxia, ptosis and diplopia, coexisting with anti-N-methyl-d-aspartate receptor antibodies. We review the literature and identify 23 other cases with brain MRI examinations to summarize the lesion locations and clinical characteristics of PDA syndrome, and ultimately provide a new framework for understanding this rare condition.The current case expands the spectrum of symptoms in PDA syndrome, which was including but not limited to dysarthria and ataxia. Caudal paramedian midbrain lesions involving decussation of the superior cerebellar peduncles appear to be critical for PDA syndrome.

A hidden mesencephalic variant of central pain

Central post-stroke pain (CPSP) can arise after lesions anywhere in the central somatosensory pathways, essentially within the spinothalamic system (STS). Although the STS can be selectively injured in the mesencephalon, CPSP has not been described in pure midbrain infarcts. Of more than 300 CPSP consecutive cases, we describe five patients who developed definite neuropathic pain following lesions circumscribed to the postero-lateral mesencephalon. The mesencephalic lesion responsible for pain was always haemorrhagic and always involved the spinothalamic tract (STT), as demonstrated by suppressed laser-evoked potentials in every case, with or without preserved lemniscal function. In three cases the midbrain injury could be ascribed to trauma, presumably from the cerebellar tentorium. As a result of the paucity of sensory symptoms, the pain was considered as 'psychogenic' in two of the patients until electrophysiological testing confirmed STT involvement. Postero-lateral midbrain lesions should be added to potential causes of CPSP. Because pain and spinothalamic deficits may be the only clinical sign, and because small lateral midbrain lesions may be difficult to trail with MRI, mesencephalic CPSP can be misdiagnosed as malingering or psychogenic pain for years. Selective spinothalamic injury caused by small lateral midbrain lesions is a very rare cause of central post-stroke pain that can remain undiagnosed for years. It appears to obey to haemorrhagic, sometimes post-traumatic lesions. Sudden development of contralateral burning pain with isolated spinothalamic deficits may be the only localizing sign, which can be easily objectively detected with electrophysiological testing.

Thalamic Ischemic Stroke as a Result of the Occlusion of the Artery of Persheron

The artery of Percheron originates from the right or left posterior cerebral artery and is one of the options for normal blood supply to the paramedian portions of the thalamus. Stroke in this area has specific MRI changes, the most informative ones in diffusion-weighted imaging mode. With the involvement of the midbrain, its pial surface can display an additional pathognomonic V-shaped sign in 67%. The clinical manifestations are non-specific. In some cases, there is a triad of symptoms, which is distinguished into paramedian thalamic syndrome (vertical gaze palsy, neuropsychological disorders, and depressed level of consciousness up to coma). The symptoms of a midbrain lesion as oculomotor nerve group diseases, contralateral hemiparesis, hemiataxia or hemianesthesia, in combination with a triad, develop a thalamopeduncular or mesencephalon thalamic syndrome. The paper presents a clinical case of a 59-year-old man who was hospitalized with acute unconsciousness, a Glasgow coma scale of 13 scores, and disorientation. A neurological examination revealed vertical gaze palsy and upper limb ataxia. Brain MRI revealed characteristic bithalamic paramedian stroke. After completing the treatment, the patient was discharged showing incomplete clinical recovery.

Dorsal midbrain involvement in MRI as a core clinical manifestation for NMOSD diagnosis

BackgroundFew data are available on the prevalence of midbrain lesions among NMOSD patients. The study aimed to address the frequency of midbrain lesions, especially dorsal midbrain involvement, among a group of NMOSD patients. MethodsThe medical records of 108 NMOSD patients were reviewed, who were registered at the Al-Zahra MS Clinic, Isfahan, Iran. The patients´ information including sex, age, first recorded chief complaint, and midbrain lesion presence in the first brain MRI was collected. ResultsOut of the 108 NMOSD patients, eight had midbrain lesions in their first brain MRI (7.4%). Of these patients, 50% were male and 50% were female, with the mean age being 35.25 ± 12.17 years. The most frequent first chief complaints included diplopia due to incomplete third nerve palsy and vertigo. The brain MRIs of the patients showed symmetric dorsal midbrain involvement in all the patients, and enhancement was discovered in only one of the brain MRIs. ConclusionAmong the patients, 7.4% presented midbrain involvement at onset. Therefore, midbrain lesions should also be considered as a possible core clinical manifestation in the NMOSD diagnostic criteria.

Atypical Neuroimaging in a Patient with Uremic Encephalopathy Showing the Bilateral Thalamus and Midbrain Lesions

Atypical Neuroimaging in a Patient with Uremic Encephalopathy Showing the Bilateral Thalamus and Midbrain Lesions

Stereotactic Brainstem Biopsy: Technical Aspects with Emphasis on Role of Awake Craniotomy

Abstract Introduction The role of frame-based stereotactic biopsy in brainstem lesions has been well established in literature. Transfrontal, transtentorial, and transcerebellar routes are used to access various targets within the brainstem. While the transfrontal approach is preferable in midbrain lesions, a transcerebellar approach via the middle cerebellar peduncle forms the shortest possible trajectory for pontine and medullary lesions. Objective Authors to describe the technical nuances of frame-based stereotactic biopsy of lower brainstem lesions to increase the procedural safety and efficacy. Materials and Methods Technical modifications in frame fixation were done to acheive the desired trajectory to the target. In adult cases biopsy was performed with patient awake during the procedure. Results Total of five patients underwent biopsy with the technical modifications. Three patients were adults and two were in pediatric age group. Their age ranged from 12 to 50 years. No complications were encountered. Two of the biopsies showed demyelination and the other three turned out to be low-grade glioma, pilocytic astrocytoma, and lymphoma, respectively. Conclusion Despite obvious inherent risks, the transcerebellar biopsy in semi-sitting position is a well-tolerated and effective method of obtaining a diagnostic tissue sample in brainstem lesions. We have noted that adoption of the technical modifications described in this article has aided in improving the safety and ease of the procedure.

Prognosis analysis of 112 cases with Japanese encephalitis in adults

Objective: To analyze the improvement of clinical symptoms and recovery of neurological function in adult Japanese encephalitis, and study the prognostic factors. Methods: Follow-up was conducted for 112 hospitalized patients with Japanese encephalitis (JE) in adults at the Department of Neurology of three hospitals in Gansu province from July to October 2016, from July to October 2017, 6 months and 1 year after onset, respectively. The neurological functional recovery was evaluated by modified Ranking Scale (mRS).The influencing factors were analyzed by logistic regression model. Results: Among the 112 adult patients with JE after 1year follow-up, 57% (64/112) were completely recovered (mRS score=0), and 14%(16/112) had mild neurological dysfunction (mRS score=1 or 2 points), 20% (22/112) had moderate to severe neurological dysfunction (mRS score 3 to 5), and 9% (10/112) died. In 102 survivors, decreased consciousness were fully recovered (100%), 75% of the mental and behavior disorders, 64% of cognitive/memory impairment, 71% of language function disorder, 61% of paralysis, 73% of extrapyramidal symptoms were fully recovered, and 92% of the seizures were controlled. Comparison of clinical data of initial on-set between good prognosis group (mRS score≤2, 80 cases) and poor prognosis group (mRS score>2, 32 cases) showed that initial clinical manifestation with seizures, consciousness (GCS score), cerebrospinal fluid pressure, and lesion of MRI involved in midbrain had statistically significant differences (all P<0.05) . Multivariate analysis demonstrated that cerebrospinal fluid (CSF) pressure>250 mmH(2)O and lesion of midbrain in MRI were independent risk factors of poor prognosis in adult patients with JE. Conclusion: JE is an acute and infectious viral encephalitis of the central nervous system with high disability and mortality. Most patients were completely recovered, and some had neurological sequelae. CSF pressure>250 mmH(2)O and lesion of midbrain in MRI are independent risk factors for poor prognosis.

A patient with nocturnal visual hallucinations.

Citation:Dholakia S. A patient with nocturnal visual hallucinations. J Clin Sleep Med. 2020;16(5):821–822.

Wernekink commissure syndrome secondary to a rare ‘V’-shaped pure midbrain infarction: a case report and review of the literature

Purpose: Wernekink commissure syndrome is a typical but extremely rare mesencephalic syndrome, and generally presents with bilateral cerebellar dysfunction, diverse oculomotor disorders and occasionally delayed-onset palatal myoclonus or tremor. However, it has been reported infrequently.Methods: We report a case of a 55-year-old man who suffered an acute paramedian midbrain infarction presenting with bilateral cerebellar ataxia, bilateral anterior internuclear ophthalmoplegia and unilateral pseudoabducens palsy, which is confirmed as Wernekink commissure syndrome by magnetic resonance imaging (MRI). We summarized the clinical data of this entity and performed a literature review of 20 previous reports of patients with this syndrome.Results: In combination with previous reports, we found that the most common symptom was bilateral cerebellar ataxia (100%) and other frequent symptoms were oculomotor disorders (81%), delayed palatal myoclonus or tremor (33%) and consciousness dysfunction (33%). Lesions on brain MRI of all patients affected the area of caudal paramedian midbrain (CPM).Conclusion: Bilateral cerebellar ataxia and lesions involved in the area of CPM on MRI are the major features of Wernekink commissure syndrome and should be the necessary conditions of diagnostic criteria. The simultaneous occurrence of bilateral cerebellar ataxia and oculomotor disorders is significant for localization diagnosis. Consciousness dysfunction is also a relatively frequent symptom of this syndrome. Moreover, pseudoabducens palsy might be attributed to a midbrain lesion. Clinicians should be familiar with and early to recognize this unique syndrome to avoid misdiagnosis.

Vestibular disorders in roll plane from brainstem to cortex

The aim is to review current knowledge of the perception of verticality, its normal function and disorders. This is based on an integrative graviceptive input from the vertical semicircular canals and the otolith organs. The focus is particularly on human psychophysics, neurophysiological and imaging data on vestibular disorders in the roll plane. The signs and symptoms are head tilt, vertical divergence of the eyes (skew deviation), ocular torsion, and tilts of subjective visual vertical (SVV) adjustments, all of which represent the so-called ocular tilt reaction (OTR). Furthermore, these signs will be related to mathematical modeling of specific vestibular cell functions for orientation in space in rodents and in patients. Pathological tilts of the SVV in the roll plane are most sensitive and frequent clinical vestibular signs of unilateral lesions extending from the labyrinths via the brainstem and thalamus to the parieto-insular vestibular cortex [[1]Brandt T. Dieterich M. The dizzy patient: Don’t forget disorders of the central vestibular system.Nat. Rev. Neurol. 2017 Jun; 13: 352-362https://doi.org/10.1038/nrneurol.2017.58Google Scholar]. Due to crossings of ascending graviceptive fibers, peripheral vestibular and pontomedullary lesions cause ipsilateral tilts of the SVV; ponto-mesencephalic lesions cause contralateral tilts. In contrast, SVV tilts, which are measured in unilateral vestibular lesions at thalamic and cortical levels, have two different characteristic features: (i) they may be ipsi- or contralateral, and (ii) they are smaller than those found in lower brainstem or peripheral lesions. Motor signs such as head tilt and body lateropulsion, i.e. components of OTR, are typical for vestibular lesions of the peripheral vestibular organ and the pontomedullary brainstem (vestibular nucleus). They are less frequent in midbrain lesions (interstitial nucleus of Cajal) and rare in cortical lesions. Vestibular function in the roll plane and its disorders can be mathematically modeled by an attractor model of the function of angular head velocity cells and head direction cells [[2]Glasauer S. Dieterich M. Brandt T. Neuronal network-based mathematical modelling of perceived verticality in acute unilateral vestibular lesions: from nerve to thalamus and cortex.J. Neurol. 2018 May 29; https://doi.org/10.1007/s00415-018-8909-5Google Scholar]. Conclusion: Clinical determinations of the SVV are easy and reliable. They indicate acute unilateral vestibular dysfunctions, the causative lesion of which extends from labyrinth to cortex. Together with additional ocular motor or brainstem signs they allow precise topographical diagnosis of side and level.

Magnetic resonance imaging findings in Parinaud's syndrome: comparing pineal mass findings to other etiologies

PurposeIn a recent study, it was found that, although intrinsic midbrain signal abnormality (IMSA) on MRI is associated with Parinaud's syndrome (PS) in patients with pineal gland masses (PM), it had no predictive value with respect to resolution of PS. We sought to compare the PM and non-pineal etiologies (NPE) of PS by reviewing imaging features of PS and whether or not they are predictive of resolution of symptoms. MethodsWe reviewed electronic medical records from 1980 to 2017 and identified 71 patients with PS from any etiology who had MR imaging: 26 with PM and 45 with NPE. We subdivided the 45 NPE patients into those with intrinsic midbrain lesions (IMBL) (n = 23) and those with extrinsic midbrain lesions (EMBL) (n = 22). PS resolution and hydrocephalus data were collected. Imaging studies were reviewed for the presence of IMSA and hydrocephalus. ResultsPS patients with EMBL were less likely to have IMSA than those with PM or IMBL (p ≤0.001). PS resolution occurred more commonly with PM than IMBL and NPE (p = 0.03, p = 0.01). For all NPE patients, resolution of PS occurred with equal frequency in patients with and without IMSA (p = 1.00). Hydrocephalus occurred more frequently in patients with PM and EMBL than IMBL (p = 0.01, p = 0.03). ConclusionsIMSA is present more often in patients with PS from PM or IMBL than in patients with EMBL. EMBL, including PM, have an increased likelihood for PS resolution. There is no predictive value of IMSA with respect to resolution of PS in NPE as well as PM.

Long‐term successful outcome of a Streptococcus equi subspecies equi brain abscess

SummaryWe previously described successful treatment, including surgical drainage, of a Streptococcus equi subspecies equi brain abscess that caused severe neurological deficits in a 7‐year‐old Quarter Horse mare. This report details the long‐term successful outcome of the case, findings of a magnetic resonance imaging (MRI) study performed 14 years after surgery and necropsy findings 18 years after initial treatment. Despite persistent cerebral and midbrain lesions detected by MRI and at necropsy, the mare returned to serviceable function within a year of initial treatment and had a successful performance career for over 10 years until carpal arthritis prompted retirement. This case demonstrates that brain abscess in horses can be successfully managed by combined medical and surgical treatment.

Perception of Verticality and Vestibular Disorders of Balance and Falls.

Objective: To review current knowledge of the perception of verticality, its normal function and disorders. This is based on an integrative graviceptive input from the vertical semicircular canals and the otolith organs.Methods: The special focus is on human psychophysics, neurophysiological and imaging data on the adjustments of subjective visual vertical (SVV) and the subjective postural vertical. Furthermore, examples of mathematical modeling of specific vestibular cell functions for orientation in space in rodents and in patients are briefly presented.Results: Pathological tilts of the SVV in the roll plane are most sensitive and frequent clinical vestibular signs of unilateral lesions extending from the labyrinths via the brainstem and thalamus to the parieto-insular vestibular cortex. Due to crossings of ascending graviceptive fibers, peripheral vestibular and pontomedullary lesions cause ipsilateral tilts of the SVV; ponto-mesencephalic lesions cause contralateral tilts. In contrast, SVV tilts, which are measured in unilateral vestibular lesions at thalamic and cortical levels, have two different characteristic features: (i) they may be ipsi- or contralateral, and (ii) they are smaller than those found in lower brainstem or peripheral lesions. Motor signs such as head tilt and body lateropulsion, components of ocular tilt reaction, are typical for vestibular lesions of the peripheral vestibular organ and the pontomedullary brainstem (vestibular nucleus). They are less frequent in midbrain lesions (interstitial nucleus of Cajal) and rare in cortical lesions. Isolated body lateropulsion is chiefly found in caudal lateral medullary brainstem lesions. Vestibular function in the roll plane and its disorders can be mathematically modeled by an attractor model of angular head velocity cell and head direction cell function. Disorders manifesting with misperception of the body vertical are the pusher syndrome, the progressive supranuclear palsy, or the normal pressure hydrocephalus; they may affect roll and/or pitch plane.Conclusion: Clinical determinations of the SVV are easy and reliable. They indicate acute unilateral vestibular dysfunctions, the causative lesion of which extends from labyrinth to cortex. They allow precise topographical diagnosis of side and level in unilateral brainstem or peripheral vestibular disorders. SVV tilts may coincide with or differ from the perception of body vertical, e.g., in isolated body lateropulsion.

Ocular Motor Dysfunction Due to Brainstem Disorders.

The brainstem contains numerous structures including afferent and efferent fibers that are involved in generation and control of eye movements. These structures give rise to distinct patterns of abnormal eye movements when damaged. Defining these ocular motor abnormalities allows a topographic diagnosis of a lesion within the brainstem. Although diverse patterns of impaired eye movements may be observed in lesions of the brainstem, medullary lesions primarily cause various patterns of nystagmus and impaired vestibular eye movements without obvious ophthalmoplegia. By contrast, pontine ophthalmoplegia is characterized by abnormal eye movements in the horizontal plane, while midbrain lesions typically show vertical ophthalmoplegia in addition to pupillary and eyelid abnormalities. Recognition of the patterns and characteristics of abnormal eye movements observed in brainstem lesions is important in understanding the roles of each neural structure and circuit in ocular motor control as well as in localizing the offending lesion.

P115. Painful mydriasis as the only clinical sign of an ipsilateral midbrain abscess

History A 39-year-old man noted increasing right frontal and right retroorbital pain. After 3 days, he also noted blurred vison in the right eye. On clinical examination, he had a mydriatic right pupil with diminished light reaction but otherwise normal findings including eye movements examination (and direct-current electro-oculography). Findings Masseter reflex testing disclosed an increased latency on the right side and was interpreted in favor of an ipsilateral mesencephalic lesion. MRI documented an abscess in the left ventral midbrain involving the region of the distal intra-mesencephalic segment of the 3rd nerve. Cerebrospinal fluid analysis revealed 185 leucocytes/ μ l, mildly elevated total protein (536 g/l), and normal glucose and lactate levels. There was no serological evidence for neuroborreliosis, neurolues, brucellosis, leptospirosis, echinococcosis, or fungal infections. Transesophageal echocardiography and dental and otolaryngological examinations were normal. Treatment He was treated with a combination of ceftriaxone (2 × 2 g/d) plus flucloxacillin (4 × 2 g/d) plus metronidazole (3 × 500 mg/d) for 6 weeks, and for another 6 weeks with cotrimoxazole (800 mg sulfamethoxazole + 160 mg trimethoprim twice daily). During the first 2 weeks antibiotic treatment was accompanied by dexamethasone (initial bolus of 40 mg i.v. followed by 4 × 8 mg/d, which was slowly tapered within 2 weeks). Clinical course Complete clinical recovery occurred within 2 weeks and CSF was normal after 15 days (4 leukoctes/ μ l, total protein: 228 g/l) Conclusion Painful unilateral mydriais may be the only clinical sign of an ipsilateral midbrain lesion.

Neuronal network-based mathematical modeling of perceived verticality in acute unilateral vestibular lesions: from nerve to thalamus and cortex.

Acute unilateral lesions of vestibular graviceptive pathways from the otolith organs and semicircular canals via vestibular nuclei and the thalamus to the parieto-insular vestibular cortex regularly cause deviations of perceived verticality in the frontal roll plane. These tilts are ipsilateral in peripheral and in ponto-medullary lesions and contralateral in ponto-mesencephalic lesions. Unilateral lesions of the vestibular thalamus or cortex cause smaller tilts of the perceived vertical, which may be either ipsilateral or contralateral. Using a neural network model, we previously explained why unilateral vestibular midbrain lesions rarely manifest with rotational vertigo. We here extend this approach, focussing on the direction-specific deviations of perceived verticality in the roll plane caused by acute unilateral vestibular lesions from the labyrinth to the cortex. Traditionally, the effect of unilateral peripheral lesions on perceived verticality has been attributed to a lesion-based bias of the otolith system. We here suggest, on the basis of a comparison of model simulations with patient data, that perceived visual tilt after peripheral lesions is caused by the effect of a torsional semicircular canal bias on the central gravity estimator. We further argue that the change of gravity coding from a peripheral/brainstem vectorial representation in otolith coordinates to a distributed population coding at thalamic and cortical levels can explain why unilateral thalamic and cortical lesions have a variable effect on perceived verticality. Finally, we propose how the population-coding network for gravity direction might implement the elements required for the well-known perceptual underestimation of the subjective visual vertical in tilted body positions.