Pure sensory syndromes in thalamic stroke

Approach to diagnosis, evaluation, and treatment of generalized and nonlocal dysesthesia: A review

Dysesthesia is an abnormal sensation in the skin that occurs in the absence of any extraordinary stimulus or other primary cutaneous disorders, excluding any delusions or tactile hallucinations. Clinicians have characterized dysesthesias to include sensations such as burning, tingling, pruritus, allodynia, hyperesthesia, or anesthesia. The etiology and pathogenesis of various generalized dysesthesias is largely unknown, though many dysesthesias have been associated with systemic pathologies including malignancy, infection, autoimmune disorders, and neuropathies. Dermatologists are often the first-line clinicians for patients presenting with such cutaneous findings, thus it is crucial for these physicians to be able to methodically work-up generalized dysesthesias to build a working differential diagnosis, follow up with key labs and/or imaging, and offer patients evidence-based treatment to relieve their symptoms. This broad literature review is an attempt to centralize key studies, cases, and series to help guide dermatologists in their assessment and evaluation of complaints of abnormal cutaneous sensations.

Topographic Mapping of Isolated Thalamic Infarcts Using Vascular and Novel Probabilistic Functional Thalamic Landmarks

Purpose

We aimed to re-evaluate the relationship between thalamic infarct (TI) localization and clinical symptoms using a vascular (VTM) and a novel functional territorial thalamic map (FTM).

Methods

Magnetic resonance imaging (MRI) and clinical data of 65 patients with isolated TI were evaluated (female n = 23, male n = 42, right n = 23, left n = 42). A VTM depicted the known seven thalamic vascular territories (VT: inferolateral, anterolateral, inferomedial, posterior, central, anteromedian, posterolateral). An FTM was generated from a probabilistic thalamic nuclei atlas to determine six functionally defined territories (FT: anterior: memory/emotions; ventral: motor/somatosensory/language; medial: behavior/emotions/nociception, oculomotor; intralaminar: arousal/pain; lateral: visuospatial/somatosensory/conceptual and analytic thinking; posterior: audiovisual/somatosensory). Four neuroradiologists independently assigned diffusion-weighted imaging (DWI) lesions to the territories mapped by the VTM and FTM. Findings were correlated with clinical features.

Results

The most frequent symptom was a hemisensory syndrome (58%), which was not specific for any territory. A co-occurrence of hemisensory syndrome and hemiparesis had positive predictive values (PPV) of 76% and 82% for the involvement of the inferolateral VT and ventral FT, respectively. Thalamic aphasia had a PPV of 63% each for involvement of the anterolateral VT and ventral FT. Neglect was associated with involvement of the inferolateral VT/ventral FT. Interrater reliability for the assignment of DWI lesions to the VTM was fair (κ = 0.36), but good (κ = 0.73) for the FTM.

Conclusion

The FTM revealed a greater reproducibility for the topographical assignment of TI than the VTM. Sensorimotor hemiparesis and neglect are predictive for a TI in the inferolateral VT/ventral FT. The hemisensory syndrome alone does not allow any topographical assignment.

Somatosensory Deficits After Stroke: Insights From MRI Studies

Somatosensory deficits after stroke are a major health problem, which can impair patients' health status and quality of life. With the developments in human brain mapping techniques, particularly magnetic resonance imaging (MRI), many studies have applied those techniques to unravel neural substrates linked to apoplexy sequelae. Multi-parametric MRI is a vital method for the measurement of stroke and has been applied to diagnose stroke severity, predict outcome and visualize changes in activation patterns during stroke recovery. However, relatively little is known about the somatosensory deficits after stroke and their recovery. This review aims to highlight the utility and importance of MRI techniques in the field of somatosensory deficits and synthesizes corresponding articles to elucidate the mechanisms underlying the occurrence and recovery of somatosensory symptoms. Here, we start by reviewing the anatomic and functional features of the somatosensory system. And then, we provide a discussion of MRI techniques and analysis methods. Meanwhile, we present the application of those techniques and methods in clinical studies, focusing on recent research advances and the potential for clinical translation. Finally, we identify some limitations and open questions of current imaging studies that need to be addressed in future research.

Rehabilitation of somatic sensation and related deficit of motor control by Mirror Box Therapy: a case report

Somatosensory disorders are often present after cerebral stroke. These deficits are associated with patients' disability. Therefore, their rehabilitation takes an importance in recovery program. However, the treatment of sensation remains poorly considered during neurorehabilitation and evidence for active sensory training is limited. Mirror Box Therapy is a simple training used to treat upper extremity motor deficits and pain also in patients with stroke. However, the effects of Mirror Box Therapy on somatosensory impairments in post-stroke patients are not deeply investigated and often exclusively motor exercises are provided during therapy.The aim of the present study was to investigate the effects of Mirror Box Therapy sensory training on somatosensory deficits in a stroke patient presenting upper limb impairment.The patient underwent to four weeks of training, five days a week. Before, during and after the Mirror Box Therapy treatment, the patient was assessed by Rivermead Assessment of Somatosensory Performance. Before and after training also upper limb motor function and performance in activities of daily living were assessed.After training patient showed an improvement in somatosensory performance. The gain was maintained at follow-up.This case report shows the effects of Mirror Box Therapy sensory training on the upper extremity for the improvement of sensation and movement in a patient with a thalamo-capsular hemorrhagic stroke during the subacute phase.

Hemisensory syndrome: Hyperacute symptom onset and age differentiates ischemic stroke from other aetiologies

Background

An important cause of hemisensory syndrome is ischemic stroke. However, the diagnostic yield of neuroradiological imaging on hemisensory syndrome is low. Therefore, we aim to describe patients hospitalized with isolated hemisensory syndrome, and to identify clinical features associated with an aetiology of ischemic stroke.

Methods

We performed a single centre retrospective observation study, identifying patients who were hospitalised with hemisensory syndrome from October 2015 to March 2016, and whom underwent a magnetic resonance imaging (MRI) brain during the admission. Ischemic stroke was defined as the presence of restricted diffusion-weighted image on the MRI brain. Clinical information was analysed and compared between patients with and without stroke seen on MRI brain.

Results

79 patients, 36 (45.6%) males and 43 (54.4%) females, aged between 30 to 87 years (mean 54), were included in the final analysis. 18 (22.8%) patients were identified to have an acute ischemic stroke. Clinical features associated with ischemic stroke in hospitalised patients with hemisensory syndrome include symptom onset of ≤24 h at presentation (odds ratio 31.4, 95% CI 3.89–254.4), advanced age (odds ratio 1.14, CI 1.05–1.25) and smoking (odds ratio 7.35, 95% CI 1.20–45).

Conclusion

Older patients, with a history of smoking, and who present with an acute onset of symptoms, are more likely to have ischemic stroke as the cause of their hemisensory syndrome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02206-8.

Implementing a Pain Assessment Survey and Team Approach Method to Effectively Assess and Treat Pain in Poststroke Patients

OBJECTIVES

To monitor and treat pain effectively in stroke patients in an inpatient rehabilitation facility using an efficient Pain Assessment Survey.

DESIGN

The study was conducted as a 2-part project. Part 1 was a preintervention study conducted to assess the prevalence of pain in poststroke patients using a Pain Assessment Survey. Factors such as central and peripheral mechanisms, psychological factors, and autonomic input were used to study the surveyed population. Other potential risk factors, such as age and sex, were also incorporated into statistical gathering. The correlation between the presence of pain and poststroke patients was assessed, and an enhanced pain assessment was created and implemented in the admission process of poststroke patients. This helped comprise part of the second portion of the study, the postintervention study.

SETTING

Participants were chosen from an inpatient rehabilitation facility. Each part of the project was conducted over a 6-month period.

PARTICIPANTS

Patients (N=184) were randomly selected. Eighty-two patients were included in the preintervention survey, and 102 patients were included in the postintervention survey. Those who had pain prior to stroke that remained unchanged or if the pain was secondary to another diagnosis were excluded from the study.

INTERVENTION

Patients with complaints of poststroke pain (PSP) were intervened immediately upon admission using a team approach. This included all personnel involved in the patient's care to resolve pain before discharge. Different types of medications and non-medical modalities were used for pain control.

MAIN OUTCOME MEASURE

The prevalence of PSP in poststroke patients.

RESULTS

The preintervention survey revealed a pain prevalence of 31.7%, whereas the postintervention study showed a prevalence of 11.8% in poststroke patients on admission. The odds that a poststroke patient would be discharged without pain and with a proper pain assessment and management was 96.2, with a statistically significant P value of .0015.

CONCLUSION

The team approach to pain management resulted in all patients being successfully treated and discharged pain free. This further demonstrates the importance of using both a pain assessment survey and team approach to assess PSP in poststroke patients.

The cornucopia of central disinhibition pain - An evaluation of past and novel concepts

Central disinhibition (CD), as applied to pain, decreases thresholds of endogenous systems. This provokes onset of spontaneous or evoked pain in an individual beyond the ability of the nervous system to inhibit pain resulting from a disease or tissue damage. The original CD concept as proposed by Craig entails a shift from the lateral pain pathway (i.e. discriminative pain processing) towards the medial pain pathway (i.e. emotional pain processing), within an otherwise neurophysiological intact environment. In this review, the original CD concept as proposed by Craig is extended by the primary "nociceptive pathway damage - CD" concept and the secondary "central pathway set point - CD". Thereby, the original concept may be transferred into anatomical and psychological non-functional conditions. We provide examples for either primary or secondary CD concepts within different clinical etiologies as well as present surrogate models, which directly mimic the underlying pathophysiology (A-fiber block) or modulate the CD pathway excitability (thermal grill). The thermal grill has especially shown promising advancements, which may be useful to examine CD pathway activation in the future. Therefore, within this topical review, a systematic review on the thermal grill illusion is intended to stimulate future research. Finally, the authors review different mechanism-based treatment approaches to combat CD pain.

A hidden mesencephalic variant of central pain

BACKGROUND

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.

METHODS

Of more than 300 CPSP consecutive cases, we describe five patients who developed definite neuropathic pain following lesions circumscribed to the postero-lateral mesencephalon.

RESULTS

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.

CONCLUSION

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.

SIGNIFICANCE

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.

Dejerine-Roussy syndrome: Historical cases

On June 7, 1906, Jules Dejerine (1849-1917) and Gustave Roussy (1874-1948) presented to the Société de Neurologie de Paris the first description of the thalamic syndrome with serial-section microscopic images. They also provided the first account of central poststroke pain (CPSP). They suggested that pain is one of the primary symptoms of the syndrome, although one of their own patients ("Hud") did not have pain. Several contemporary studies have highlighted the involvement of the anterior part of the pulvinar (PuA) in patients with CPSP of thalamic origin. Two historical observations (cases Jos and Hud) are reviewed here using the Morel nuclei staining atlas (2007). Dejerine and Roussy proposed the "irritative theory" to explain CPSP of thalamic origin and, in line with the most recent literature, they invoked the involvement of the PuA. When matching images for the Jos and Hud cases with the Morel atlas, it appears that the lesions involved what Dejerine then termed the noyau externe; that is, the ventral posterolateral nucleus and the PuA. In the Jos case, the lesion extended medially to what Dejerine termed the noyau médian de Luys; that is, the central medial-parafascicular nuclei, whereas in the Hud case the lesion extended more inferiorly. From the finding in the Hud case, one can hypothesize that impairment of the PuA alone does not assure pain. The work of Dejerine and Roussy, based on clinico-anatomical correlations, remains relevant to this day.

['Stroke chameleons']

The diagnosis of acute stroke should be correct and early that allows physician planning the most effective treatment strategies (reperfusion therapy, undifferentiated (basic) treatment, early secondary prevention). However, stroke symptoms can be atypical and similar to some other (non-vascular) event. It can significantly complicate the clinical diagnosis of stroke and decrease the patient's chances for effective treatment. A stroke should be suspected in every patient with acute onset of neurological symptoms, especially when the patient has the 'vascular' risk factors. Furthermore it is important to remember that negative CT-scan data and/or MRI data do not exclude the presence of not only ischemic stroke but also hemorrhagic stroke. The article describes the main variants of strokes with atypical symptoms (strokes-chameleons), emphasizes the importance of careful clinical examination, provides supportive differential diagnostic criteria and discusses limitations of neuroimaging methods.

Somatosensory deficits

The analysis and interpretation of somatosensory information are performed by a complex network of brain areas located mainly in the parietal cortex. Somatosensory deficits are therefore a common impairment following lesions of the parietal lobe. This chapter summarizes the clinical presentation, examination, prognosis, and therapy of sensory deficits, along with current knowledge about the anatomy and function of the somatosensory system. We start by reviewing how somatosensory signals are transmitted to and processed by the parietal lobe, along with the anatomic and functional features of the somatosensory system. In this context, we highlight the importance of the thalamus for processing somatosensory information in the parietal lobe. We discuss typical patterns of somatosensory deficits, their clinical examination, and how they can be differentiated through a careful neurologic examination that allows the investigator to deduce the location and size of the underlying lesion. In the context of adaption and rehabilitation of somatosensory functions, we delineate the importance of somatosensory information for motor performance and the prognostic evaluation of somatosensory deficits. Finally, we review current rehabilitation approaches for directing cortical reorganization in the appropriate direction and highlight some challenging questions that are unexplored in the field.

Deep brain stimulation for stroke: Current uses and future directions

BACKGROUND

Survivors of stroke often experience significant disability and impaired quality of life related to ongoing maladaptive responses and persistent neurologic deficits. Novel therapeutic options are urgently needed to augment current approaches. One way to promote recovery and ameliorate symptoms may be to electrically stimulate the surviving brain. Various forms of brain stimulation have been investigated for use in stroke, including deep brain stimulation (DBS).

OBJECTIVE/METHODS

We conducted a comprehensive literature review in order to 1) review the use of DBS to treat post-stroke maladaptive responses including pain, dystonia, dyskinesias, and tremor and 2) assess the use and potential utility of DBS for enhancing plasticity and recovery from post-stroke neurologic deficits.

RESULTS/CONCLUSIONS

A large variety of brain structures have been targeted in post-stroke patients, including motor thalamus, sensory thalamus, basal ganglia nuclei, internal capsule, and periventricular/periaqueductal grey. Overall, the reviewed clinical literature suggests a role for DBS in the management of several post-stroke maladaptive responses. More limited evidence was identified regarding DBS for post-stroke motor deficits, although existing work tentatively suggests DBS-particularly DBS targeting the posterior limb of the internal capsule-may improve paresis in certain circumstances. Substantial future work is required both to establish optimal targets and parameters for treatment of maladapative responses and to further investigate the effectiveness of DBS for post-stroke paresis.

Thalamic transitory ischemic attacks presenting as Jacksonian sensory march

Spreading somatosensory symptoms appearing as Jacksonian sensory march are usually considered to be due to an epileptic seizure. We report on three cases in which these symptoms were caused by thalamic ischemia. Two patients presented with stereotypically recurring hemiparesthesias lasting 2-5 min that gradually spread from the face to the arm and leg on one side. A first cerebral magnetic resonance imaging including DWI was negative in both cases, whereas new thalamic infarctions appeared on repeated imaging when clinical symptoms remained. A third case with a thalamic ischemia did not show recurring events, but also presented with purely sensory spreading symptoms. In all three cases EEG and cardiovascular diagnostics revealed normal results. Pure sensory stroke has previously been described as a result of ischemia of the thalamus or the internal capsule presenting as a sudden onset hemisensory deficit, but spreading symptoms have rarely been reported. According to our observations, thalamic TIAs are an important differential diagnosis of somatosensory epileptic auras presenting with Jacksonian sensory march which require a different clinical management.

Demystifying Poststroke Pain: From Etiology to Treatment

Pain after stroke is commonly reported but often incompletely managed, which prevents optimal recovery. This situation occurs in part because of the esoteric nature of poststroke pain and its limited presence in current discussions of stroke management. The major specific afflictions that affect patients with stroke who experience pain include central poststroke pain, complex regional pain syndrome, and pain associated with spasticity and shoulder subluxation. Each disorder carries its own intricacies that require specific approaches to treatment and understanding. This review aims to present and clarify the major pain syndromes that affect patients who have experienced a stroke in order to aid in their diagnosis and treatment.

Thalamic pain: anatomical and physiological indices of prediction

Thalamic pain is a severe and treatment-resistant type of central pain that may develop after thalamic stroke. Lesions within the ventrocaudal regions of the thalamus carry the highest risk to develop pain, but its emergence in individual patients remains impossible to predict. Because damage to the spino-thalamo-cortical system is a crucial factor in the development of central pain, in this study we combined detailed anatomical atlas-based mapping of thalamic lesions and assessment of spinothalamic integrity using quantitative sensory analysis and laser-evoked potentials in 42 thalamic stroke patients, of whom 31 had developed thalamic pain. More than 97% of lesions involved an area between 2 and 7 mm above the anterior-posterior commissural plane. Although most thalamic lesions affected several nuclei, patients with central pain showed maximal lesion convergence on the anterior pulvinar nucleus (a major spinothalamic target) while the convergence area lay within the ventral posterior lateral nucleus in pain-free patients. Both involvement of the anterior pulvinar nucleus and spinothalamic dysfunction (nociceptive thresholds, laser-evoked potentials) were significantly associated with the development of thalamic pain, whereas involvement of ventral posterior lateral nucleus and lemniscal dysfunction (position sense, graphaesthesia, pallaesthesia, stereognosis, standard somatosensory potentials) were similarly distributed in patients with or without pain. A logistic regression model combining spinothalamic dysfunction and anterior pulvinar nucleus involvement as regressors had 93% sensitivity and 87% positive predictive value for thalamic pain. Lesion of spinothalamic afferents to the posterior thalamus appears therefore determinant to the development of central pain after thalamic stroke. Sorting out of patients at different risks of developing thalamic pain may be achievable at the individual level by combining lesion localization and functional investigation of the spinothalamic system. As the methods proposed here do not need complex manipulations, they can be added to routine patients' work up, and the results replicated by other investigators in the field.

Gabapentinoid Insensitivity after Repeated Administration is Associated with Down-Regulation of the α(2)δ-1 Subunit in Rats with Central Post-Stroke Pain Hypersensitivity

The α2δ-1 subunit of the voltage-gated Ca(2+) channel (VGCC) is a molecular target of gabapentin (GBP), which has been used as a first-line drug for the relief of neuropathic pain. GBP exerts its anti-nociceptive effects by disrupting trafficking of the α2δ-1 subunit to the presynaptic membrane, resulting in decreased neurotransmitter release. We previously showed that GBP has an anti-allodynic effect in the first two weeks; but this is followed by insensitivity in the later stage after repeated administration in a rat model of central post-stroke pain (CPSP) hypersensitivity induced by intra-thalamic hemorrhage. To explore the mechanisms underlying GBP insensitivity, the cellular localization and time-course of expression of the α2δ-1 subunit in both the thalamus and spinal dorsal horn were studied in the same model. We found that the α2δ-1 subunit was mostly localized in neurons, but not astrocytes and microglia. The level of α2δ-1 protein increased in the first two weeks after injury but then decreased in the third week, when GBP insensitivity occurred. Furthermore, the α2δ-1 down-regulation was likely caused by later neuronal loss in the injured thalamus through a mechanism other than apoptosis. In summary, the present results suggest that the GBP receptor α2δ-1 is mainly expressed in thalamic neurons in which it is up-regulated in the early stage of CPSP but this is followed by dramatic down-regulation, which is likely associated with GBP insensitivity after long-term use.

Multiple variant type thalamic infarcts: pure and combined types

BACKGROUND AND PURPOSE

Variant topographic patterns of thalamic infarction with distinct manifestations have been classified into three territories: anteromedian, central, and posterolateral. The purpose of this study was to determine clinical, etiological, and radiological features of multiple variant thalamic infarcts.

METHODS

We reviewed 8400 patients with a first clinical stroke included in the Ege Stroke Registry between 2000 and 2013. Among 80 patients with an acute multiple thalamic infarcts confirmed by MRI, we selected all patients with lesions outside the classical territories and studied their clinical, etiological, and radiological features.

RESULTS

Among 8400 patients with first-ever stroke in our registry, 21 patients (26% of all multiple thalamic infarcts) showed infarction outside the classical territories, allowing us to delineate three variant distributions; (i) unilateral multiple variant infarcts [seven patients (9%) in the anteromedian, central, and posterolateral territories] presented with predominantly decreased vigilance (66% with right lesions, 75% with left lesions), cognitive impairment including amnesia (71%), aphasia (57%) in left-sided or bilateral lesions, and executive dysfunction (43%). The most frequent stroke mechanism was cardioembolism (43%). (ii) Bilateral multiple variant infarcts [five patients (6%)], with lesions on the variant territories of the thalamus, resulting in a variety of neurological and neuropsychological signs, consciousness disturbances (80%), sensory-motor deficits (80%). Cardioembolism (60%) was the most frequent etiology. (iii) Combined multiple variant and classical infarcts [nine patients (11%)], characterized by hemihypesthesia (89%) as the most frequent manifestation, followed by hemiataxia (78%), and cognitive deficits. Cardioembolism (56%) and large-artery disease of the vertebrobasilar system (33%) were the main stroke mechanisms.

CONCLUSIONS

We described multiple variant topographic patterns of thalamic infarction with distinct manifestations and etiologies. We thought that multiple variant infarcts are the result of variation in thalamic arterial supply or reflect a source of embolism.

Post-stroke pain hypersensitivity induced by experimental thalamic hemorrhage in rats is region-specific and demonstrates limited efficacy of gabapentin

Intractable central post-stroke pain (CPSP) is one of the most common sequelae of stroke, but has been inadequately studied to date. In this study, we first determined the relationship between the lesion site and changes in mechanical or thermal pain sensitivity in a rat CPSP model with experimental thalamic hemorrhage produced by unilateral intra-thalamic collagenase IV (ITC) injection. Then, we evaluated the efficacy of gabapentin (GBP), an anticonvulsant that binds the voltage-gated Ca(2+) channel α2δ and a commonly used anti-neuropathic pain medication. Histological case-by-case analysis showed that only lesions confined to the medial lemniscus and the ventroposterior lateral/medial nuclei of the thalamus and/or the posterior thalamic nucleus resulted in bilateral mechanical pain hypersensitivity. All of the animals displaying CPSP also had impaired motor coordination, while control rats with intra-thalamic saline developed no central pain or motor deficits. GBP had a dose-related anti-allodynic effect after a single administration (1, 10, or 100 mg/kg) on day 7 post-ITC, with significant effects lasting at least 5 h for the higher doses. However, repeated treatment, once a day for two weeks, resulted in complete loss of effectiveness (drug tolerance) at 10 mg/kg, while effectiveness remained at 100 mg/kg, although the time period of efficacious analgesia was reduced. In addition, GBP did not change the basal pain sensitivity and the motor impairment caused by the ITC lesion, suggesting selective action of GBP on the somatosensory system.

Pure sensory syndromes and post-stroke pain secondary to bilateral thalamic lacunar infarcts: a case report

Introduction

Patients often complain about sensory symptoms that appear to the doctor as harmless, and reassurances are often given. Sensory strokes may easily be ignored.

Case presentation

A 48-year-old Caucasian woman with insulin-dependent diabetes and hyperlipidemia experienced symptoms that progressed within hours to a complete left-sided hemisensory syndrome. This was caused by a lacunar infarct in the ventral posterior tier nuclei of the right thalamus. A few days later she gradually developed an almost identical, but incomplete hemisensory syndrome on the opposite side caused by a corresponding lacune in the left thalamus. Severe persistent and paroxysmal pain on both sides of the body became disabling.

Conclusion

Small strokes only affecting the somatosensory system should not be underestimated. Neuropathic pain may result. Probably unique in the present case is the demonstration of bilateral thalamic pain secondary to two almost identical thalamic infarcts. Small vessel disease (microatheroma or lipohyalinosis) was the most likely cause of the lacunes. One can only speculate if there was an occlusion in two separate thalamic perforators, or in a single dominant artery supplying the bilateral thalami.

Hemiparesthesias in lacunar pontine ischemic stroke

Isolated paresthesia, or paresthesia not accompanied by sensory and/or motor deficits, is an extremely rare manifestation of a cerebrovascular accident. Lacunar pure sensory stroke (PSS) confined to thalamus is characterized by persistent or transient numbness, tingling, pain, burning, or another unpleasant sensation on one side of the body. However, in this condition a sensory loss to all primary modalities in the contralateral face and body is very often encountered. Also previous reported cases of PSS due to lacunar stroke in regions other than thalamus are characterized by the presence of sensory loss together with positive sensory symptoms, none of them reporting isolated paresthesia as the only clinical feature of PSS. We present a case of isolated paresthesia as only clinical manifestation of a lacunar PSS involving both trigeminal and medial lemniscus in dorsal paramedian pontine region. A PSS manifesting with isolated paresthesias may be secondary not only to a thalamic lacunar stroke, but also to a small ischemic lesion confined to both trigeminal and medial lemniscus in dorsal paramedian pontine region.

Atypical presentations of acute cerebrovascular syndromes

Correct diagnosis of acute stroke is of paramount importance to clinicians to enable selection of correct treatments and to ensure prevention of acute complications, including recurrent stroke. Timely diagnosis can be difficult in some cases because patients with acute stroke can present with atypical or uncommon symptoms that suggest another cause altogether. Publications on these patients suggest that the following strategies could help to reduce misdiagnosis. First, clinicians should suspect stroke in any patient with abrupt onset of neurological symptoms. Second, clinicians should be aware that some patients will initially present with various uncommon and atypical stroke symptoms. Third, a complete and systematic neurological examination should be routinely done in patients presenting with acute neurological symptoms because this might shed light on the true nature of the problem. Finally, clinicians should be aware that even with the most sophisticated neuroimaging tests, stroke might be missed in the early hours after the event.

Operculo-insular pain (parasylvian pain): a distinct central pain syndrome

Central pain with dissociated thermoalgesic sensory loss is common in spinal and brainstem syndromes but not in cortical lesions. Out of a series of 270 patients investigated because of somatosensory abnormalities, we identified five subjects presenting with central pain and pure thermoalgesic sensory loss contralateral to cortical stroke. All of the patients had involvement of the posterior insula and inner parietal operculum. Lemniscal sensory modalities (position sense, graphaestesia, stereognosis) and somatosensory evoked potentials to non-noxious inputs were always preserved, while thermal and pain sensations were profoundly altered, and laser-evoked potentials to thermo-nocoiceptive stimuli were always abnormal. Central pain resulting from posterior parasylvian lesions appears to be a distinct entity that can be identified unambiguously on the basis of clinical, radiological and electrophysiological data. It presents with predominant or isolated deficits for pain and temperature sensations, and is paradoxically closer to pain syndromes from brainstem lesions affecting selectively the spinothalamic pathways than to those caused by focal lesions of the posterior thalamus. The term 'pseudo-thalamic' is therefore inappropriate to describe it, and we propose parasylvian or operculo-insular pain as appropriate labels. Parasylvian pain may be extremely difficult to treat; the magnitude of pain-temperature sensory disturbances may be prognostic for its development, hence the importance of early sensory assessment with quantitative methods.

Lacunar stroke

Lacunar infarcts or small subcortical infarcts result from occlusion of a single penetrating artery and account for one quarter of cerebral infarctions. Patients with a lacunar infarct usually present with a classical lacunar syndrome (pure motor hemiparesis, pure sensory syndrome, sensorimotor stroke, ataxic hemiparesis or dysarthria-clumsy hand) and, less frequently, an atypical lacunar syndrome. Hypertension and diabetes mellitus are major risk factors for lacunar stroke. Lacunar infarcts show a paradoxical clinical course with a favorable prognosis in the short term, characterized by a low early mortality and reduced functional disability on hospital discharge, but with an increased risk of death, stroke recurrence and dementia in the mid- and long term. Asymptomatic progression of small-vessel disease is a typical feature of the lacunar infarcts. For this reason, lacunar infarction should be regarded as a potentially severe condition rather than a relatively benign disorder and, therefore, lacunar stroke patients require adequate and rigorous management and follow-up. Antiplatelet drugs, careful blood pressure control, the use of statins and modification of lifestyle risk factors are key elements in secondary prevention after lacunar stroke.

Clinical study of 99 patients with pure sensory stroke

OBJECTIVE

We report a clinical description of pure sensory stroke based on data collected from a prospective acute stroke registry.

METHODS

From 2500 acute stroke patients included in a hospital-based prospective stroke registry over a 12-year period, 99 were identified as having pure sensory stroke.

RESULTS

Pure sensory stroke accounted for 4.7% of all acute stroke patients, 5.4% of acute ischemic stroke, and 17.4% of lacunar syndromes. Complete hemisensory syndrome was present in 80 patients and incomplete hemisensory syndrome in 19 (cheiro-oral syndrome 12, cheiro-oral-pedal 6, isolated oral syndrome 1). The lacunar hypothesis was fulfilled in 88% of patients. Atherothrombotic infarction occurred in 8 patients, intracerebral hemorrhage in 3, and stroke of undetermined cause in 1. Hemorrhagic pure sensory stroke was diagnosed in 1% of all cases of hemorrhagic stroke (n = 270) in the database. Outcome was good (in-hospital mortality 0%, symptom-free at discharge 41.5%). After multivariate analysis, absence of disability at discharge, hypertension, diabetes, hyperlipidemia, and thalamic (56.5%) and corona radiata (4%) locations were clinical and topographic variables significantly associated with pure sensory stroke.

CONCLUSIONS

Pure sensory stroke is an infrequent cerebrovascular syndrome, in which the lacunar hypothesis is supported. Most patients had thalamic lacunar infarction. Incomplete hemisensory syndromes were also caused by a lacunar infarct in 84% of patients. Hemorrhagic pure sensory stroke accounted only for 3% of the cases. The prognosis is good with striking similarity to other lacunar strokes. There are important differences between pure sensory stroke and nonlacunar strokes.

Cortical origin of functional recovery in the somatosensory cortex of the adult mouse after thalamic lesion

To study the degree and time course of the functional recovery in the somatosensory cortex (SI) after an excitotoxic lesion in the adult mouse thalamus, metabolic activity was determined in SI at various times points post-lesion. Immediately after the lesion, metabolic activity in the thalamically deafferented part of SI was at its lowest value but increased progressively at subsequent time points. This was seen in all cortical layers; however, layers I and Vb recovered more rapidly than layers II, III, IV, Va and VI. Removal of the mystacial whiskers corresponding to the deafferented area, 5 weeks after cortical recovery, produced a subsequent 32% drop in metabolic activity, demonstrating peripheral sensory activation of this part of the cortex. Tracing experiments revealed that the deafferented cortex did not receive a novel thalamic input but that cortico-cortical and contralateral barrel cortex projections to this area were reinforced. We conclude that the cortical functional recovery after a thalamic lesion is, at least partially, due to modified cortico-cortical and callosal projections to the deafferented cortical area.

Anteromedian, central, and posterolateral infarcts of the thalamus: three variant types

BACKGROUND AND PURPOSE

Thalamic infarcts have traditionally been classified into 4 territories: anterior, paramedian, inferolateral, and posterior. The purpose of this study was to review this classical versus variant distribution in patients with thalamic stroke.

METHODS

We reviewed all patients with a first clinical stroke included in the Lausanne Stroke Registry between 1990 and 2002. Among 71 patients with an acute stroke isolated to the thalamus confirmed by MRI, we selected all patients with lesions outside the classical territories and studied their clinical, etiological, and radiological features.

RESULTS

A total of 21 patients (30% of all thalamic stroke patients) showed infarction outside the classical territories, allowing us to delineate 3 variant distributions: (1) Anteromedian territory (9 patients [13%]) involving anterior and paramedian territories, with predominantly cognitive impairment, including executive dysfunction, anterograde amnesia, and aphasia in left-sided or bilateral lesions. The most frequent stroke mechanism was cardiac embolism. (2) Central territory (4 patients [6%]), with lesions on the central part of the thalamus, resulting in a variety of neurological and neuropsychological signs, reflecting the involvement of several adjacent structures. Microangiopathy was the most frequent etiology. (3) Posterolateral territory (8 patients [11%]), involving inferolateral and posterior territories, with hemihypesthesia as the most frequent manifestation, followed by hemiataxia, executive dysfunction, and aphasia in left-sided lesions. Artery-to-artery embolism and microangiopathy were the main stroke mechanisms.

CONCLUSIONS

We describe 3 variant topographic patterns of thalamic infarction with distinct manifestations and etiologies. We postulate that these infarcts are the result of a variation in thalamic arterial supply or reflect borderzone ischemia.

Hemisensory syndrome is associated with a low diagnostic yield and a nearly uniform benign prognosis

OBJECTIVE

To describe the diagnostic yield and prognosis for patients with hemisensory syndrome.

BACKGROUND

The aetiology, utility of diagnostic procedures, and outcome of hemisensory syndrome in patients with exclusive hemibody complaints having only subjective sensory abnormalities on examination is unknown.

METHODS

Patients were prospectively identified with hemisensory syndrome in a tertiary care institution from 1998-2002. Diagnostic procedures were analysed for sensitivity and clinical follow up was performed.

RESULTS

Thirty four patients, 25 (74%) women, of age 35 (SD 11) years were identified. The hemisensory syndrome occurred on the left side in 23 (68%) cases. Neuroimaging of the brain demonstrated diagnostic abnormalities representing ischaemic aetiology in one case. Other diagnostic testing including cerebrospinal fluid examination, electrophysiological testing, carotid ultrasonography, echocardiography, and blood testing revealed no diagnostic abnormalities. Sixteen patients (47%) continued to complain of hemisensory difficulties after all investigations were completed at 9.6 (5.8) days. One patient with a history of systemic lupus erythematosus and positive antiphospholipid antibodies had a second event diagnosed as stroke seven months after presentation. Clinical follow up at 16 (7) months revealed persisting symptoms in 6 (20%) of 30 patients. Six (50%) of 12 patients agreeing to psychiatric assessment received diagnoses of personality or mood disorders.

CONCLUSIONS

Diagnostic yield in hemisensory syndrome is low, and prognosis is almost always uniformly benign. The author advocates careful assessment of medical history and consideration for neuroimaging in this group of patients.

Unilateral pure thalamic asterixis: clinical, electromyographic, and topographic patterns

Eleven patients (nine with infarctions and two with primary hematomas) with isolated thalamic lesions and contralateral asterixis were examined using a standard electromyographic and neuroimaging protocol. Asterixis was a short-duration phenomenon associated with a hemiataxia hypesthesia syndrome in all patients. Electromechanical synchronization was constant for the two silent period types. The anatomic data strongly suggest that ventral lateral or lateral posterior thalamus are concerned in the pathophysiology of thalamic asterixis.

Lenticulocapsular hemorrhages presenting as pure sensory stroke

Pure sensory stroke (PSS) syndrome is most often produced by a small infarct involving the lateral thalamus. Larger than lacune-sized putaminal hemorrhages have not been considered as a cause of this syndrome. The author describes 3 patients with hypertensive lenticulocapsular hemorrhage presenting with hemisensory symptoms without any other neurological deficits. In these patients, the sensory symptoms were more marked and persistent in the legs than in the other body parts. Neuroradiological data suggested that thalamocortical sensory pathways were exclusively involved. These patients highlight the heterogeneity of the vascular lesion producing PSS syndrome and illustrate that a putaminal hemorrhage should be included in the differential diagnosis of this clinical syndrome.