Localized Reversible Reduction of Apparent Diffusion Coefficient in Transient Hypoglycemia-Induced Hemiparesis

An elderly man with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) without neuropsychiatric sequelae

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is less common in the elderly, and most have some sequelae. However, even in the elderly, MERS may have a good prognosis, and a specific treatment is not always required.

Severe Hypoglycemia Increases Dementia Risk and Related Mortality: A Nationwide, Population-based Cohort Study

CONTEXT

There are few studies focused on the relationship between hypoglycemia and new-onset dementia in patients with type 2 diabetes and no study regarding mortality of dementia after hypoglycemia.

OBJECTIVE

We investigated the effect of severe hypoglycemia on dementia subtypes and its relation to overall mortality in patients with type 2 diabetes.

METHODS

We evaluated incident dementia, including Alzheimer disease and vascular dementia, among health checkup participants aged 40 years or older in the National Health Insurance System in Korea from January 2009 to December 2015. Episodes of severe hypoglycemia were examined for 3 years before the date of the health checkup.

RESULTS

Among 2 032 689 participants (1 172 271 men, 860 418 women), 14 443 (0.7%) experienced severe hypoglycemia, during a mean follow-up period of 6.9 ± 1.7 years. Individuals in the severe hypoglycemia group were more likely to be diagnosed with dementia compared to individuals without severe hypoglycemia (23.3% vs 7.3%; P < .001) and the overall incidence of Alzheimer disease was higher than vascular dementia. Dementia risk rose with increasing number of severe hypoglycemic episodes (1 episode [hazard ratio (HR) = 1.54; 95% CI, 1.48-1.60], 2 or more episodes [HR = 1.80; 95% CI, 1.66-1.94]). Overall mortality was higher in participants with dementia, but without severe hypoglycemia (HR = 2.03; 95% CI, 1.96-2.10) and severe hypoglycemia, but without dementia (HR = 4.24; 95% CI, 4.29-4.40), and risk of death was highest in those with both severe hypoglycemia and dementia (HR = 5.08; 95% CI, 4.83-5.35).

CONCLUSION

Severe hypoglycemia is associated with dementia, especially Alzheimer disease and mortality; together, they have an additive effect on overall mortality.

Left Hemiplegia Possibly Due to Glucose Reperfusion Injury after Recovery of Severe Hypoglycemia in a Woman with Type 2 Diabetes Mellitus

A 79-year-old woman with type 2 diabetes receiving insulin was rushed to our hospital due to severe hypoglycemia. Glucose was administered, and the consciousness disturbance was promptly improved. A few hours later, conjugate deviation of the eyes to the right and left hemiplegia occurred at a normal glucose level. Cerebral magnetic resonance imaging (MRI) showed hyperintensities of the right posterior limb of the internal capsule and the medial thalamus on diffusion-weighted imaging sequences. However, the changes observed using MRI disappeared completely on the third day, and her symptoms subsequently improved. This may have been a case of glucose reperfusion injury.

Reversible Splenial Lesion Syndrome with Some Novel Causes and Clinical Manifestations

Objective Reversible splenial lesion syndrome (RESLES) is a clinical radiological syndrome characterized by a reversible lesion of the splenium of the corpus callosum with a decreased apparent diffusion coefficient (ADC) value. The clinical manifestations of RESLES are diverse. Methods Fifteen cases of adult RESLES patients (10 males and 5 females) were retrospectively selected from the radiology system using the key word "corpus callosum" at a university-affiliated tertiary care hospital between May 1, 2015 and December 31, 2019. The possible precipitating factors, clinicoradiological findings and modified Rankin Scale (mRS) on follow-up were then analyzed. Results The patient ages ranged from 22 to 53 years old. The mean age was 34 years old. The most common neurological symptoms included headache (3/15), dizziness (3/15), first onset of seizure (3/15), paroxysmal blurred vision (2/15), vertigo (2/15), amnesia (2/15), and confused consciousness without seizure (2/15), followed by drowsiness (1/15), paresthesia (1/15), dysmetria (1/15) and dysarthria (1/15). The precipitating factors included infection, seizure, anti-epileptic treatment with levetiracetam, carbamazepine, valproate, hyperglycemia, hypoglycemia, cerebral venous sinus thrombosis, and rabies vaccine injection prior to the onset of RESLES. All cases were carefully followed up and had excellent prognoses. Conclusion RESLES manifests as variety of symptoms with less specificity and precipitating factors. Paroxysmal blurred vision may be a relatively specific symptom of RESLES. Levetiracetam, carbamazepine or valproate could be the cause of RESLES, exposure to the rabies vaccine could be another predisposing factors for RESLES as well. RESLES type 1 was therefore found to be highly "reversible" with an excellent prognosis.

Mitochondrial respiratory chain deficiency correlates with the severity of neuropathology in sporadic Creutzfeldt-Jakob disease

Mitochondrial dysfunction has been implicated in multiple neurodegenerative diseases but remains largely unexplored in Creutzfeldt-Jakob disease. Here, we characterize the mitochondrial respiratory chain at the individual neuron level in the MM1 and VV2 common molecular subtypes of sporadic Creutzfeldt-Jakob disease. Moreover, we investigate the associations between the mitochondrial respiratory chain and neuropathological markers of the disease.Brain tissue from individuals with sporadic Creutzfeldt-Jakob disease and age-matched controls were obtained from the brain collection of the Austrian Creutzfeldt-Jakob Surveillance. The mitochondrial respiratory chain was studied through a dichotomous approach of immunoreactivities in the temporal cortex and the hippocampal subregions of CA4 and CA3.We show that profound deficiency of all mitochondrial respiratory complexes (I-V) occurs in neurons of the severely affected temporal cortex of patients with Creutzfeldt-Jakob disease. This deficiency correlates strongly with the severity of neuropathological changes, including vacuolation of the neuropil, gliosis and disease associated prion protein load. Respiratory chain deficiency is less pronounced in hippocampal CA4 and CA3 regions compared to the temporal cortex. In both areas respiratory chain deficiency shows a predilection for the MM1 molecular subtype of Creutzfeldt-Jakob disease.Our findings indicate that aberrant mitochondrial respiration could be involved early in the pathogenesis of sporadic Creutzfeldt-Jakob disease and contributes to neuronal death, most likely via ATP depletion. Based on these results, we propose that the restricted MRI diffusion profile seen in the brain of patients with sporadic Creutzfeldt-Jakob disease might reflect cytotoxic changes due to neuronal respiratory chain failure and ATP loss.

Pathophysiology and aetiology of hypoglycaemic crises

Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications.

Severe Hypoglycemia-induced Right Hemiparesis with Reversible Diffusion Restriction in the Left Internal Capsule Due to Combination Therapy Using Disopyramide and Clarithromycin

Severe hypoglycemia is known to cause acute focal neurological symptoms. In cases with a medical history of diabetes mellitus (DM), the diagnosis and treatment of hypoglycemia-induced neurological symptoms are simple. However, severe hypoglycemia can occur in patients who are not taking hypoglycemic agents such as insulin or long-acting sulfonylurea drugs. We describe a 95-year-old man with sudden onset of right hemiparesis who showed high signal intensity on diffusion-weighted imaging involving the left internal capsule with corresponding reduced apparent diffusion coefficient hypointensity. Laboratory findings revealed severe hypoglycemia (27 mg/dl). However, he was not taking insulin or long-acting sulfonylurea drugs but disopyramide and clarithromycin had been administered. In addition, he had kidney dysfunction with an estimated glomerular filtration rate (GFR) of 42.9 ml/min/1.73 m². After the blood glucose level was normalized, the left hemiparesis completely recovered and abnormal findings of magnetic resonance imaging (MRI) study also became normal. A combination of disopyramide and clarithromycin may cause severe hypoglycemia-induced neurological symptoms particularly in patients with kidney dysfunction. Even in a patient with sudden-onset hemiparesis and no history of DM, the possibility of hypoglycemia-induced neurological deficit should be considered.

Cytotoxic Lesions of the Corpus Callosum That Show Restricted Diffusion: Mechanisms, Causes, and Manifestations

Cytotoxic lesions of the corpus callosum (CLOCCs) are secondary lesions associated with various entities. CLOCCs have been found in association with drug therapy, malignancy, infection, subarachnoid hemorrhage, metabolic disorders, trauma, and other entities. In all of these conditions, cell-cytokine interactions lead to markedly increased levels of cytokines and extracellular glutamate. Ultimately, this cascade can lead to dysfunction of the callosal neurons and microglia. Cytotoxic edema develops as water becomes trapped in these cells. On diffusion-weighted magnetic resonance (MR) images, CLOCCs manifest as areas of low diffusion. CLOCCs lack enhancement on contrast material-enhanced images, tend to be midline, and are relatively symmetric. The involvement of the corpus callosum typically shows one of three patterns: (a) a small round or oval lesion located in the center of the splenium, (b) a lesion centered in the splenium but extending through the callosal fibers laterally into the adjacent white matter, or (c) a lesion centered posteriorly but extending into the anterior corpus callosum. CLOCCs are frequently but not invariably reversible. Their pathologic mechanisms are discussed, the typical MR imaging findings are described, and typical cases of CLOCCs are presented. Although CLOCCs are nonspecific with regard to the underlying cause, additional imaging findings and the clinical findings can aid in making a specific diagnosis. Radiologists should be familiar with the imaging appearance of CLOCCs to avoid a misdiagnosis of ischemia. When CLOCCs are found, the underlying cause of the lesion should be sought and addressed. ^©RSNA, 2017 An earlier incorrect version of this article appeared online. This article was corrected on February 13, 2017.

Localized reversible high signal intensities on diffusion-weighted MRI in hypoglycemia: A study of 70 cases

INTRODUCTION

It is well-known that localized reversible high signal intensities in the splenium of the corpus callosum or the basal ganglia appear on diffusion-weighted MRI in the presence of hypoglycemia. The aim of this study was to clarify the incidence and significance of such high signal intensity lesions.

RESULTS

We analyzed 70 cases of hypoglycemia with consciousness disturbance referred to our outpatient office. Localized reversible high signal intensities on diffusion-weighted MRI were noted in 6 cases (8.6%). They were at the splenium of the corpus callosum in four cases (5.7%), and right frontal cortex and bilateral frontal white matter in one each. Convulsions were noted in five cases, and right hemiparesis was noted in three. None of the three cases of hemiparesis showed localized reversible high signal intensities on diffusion-weighted MRI. These lesions are reversible if the patients undergo treatment without delay.

CONCLUSION

The significance of these lesions is still unclear. However, when a high signal intensity lesion that is not reasonable for the symptom is detected on diffusion-weighted MRI, an immediate check of the blood sugar level is mandatory.

Reversible splenium diffusion weighted MRI changes associated with hypoglycemia

Hypoglycemia can manifest as a stroke. MRI diffusion-weighted imaging is the most useful technique in diagnosing early ischemic injury. We report two cases of transient MRI lesions of the splenium of the corpus callosum related to hypoglycemia. Clinicians must be aware of such cases to avoid misdiagnosis.

Hypoglycemia with focal neurological signs as stroke mimic: Clinical and neuroradiological characteristics

Our aim was to investigate the clinical and radiological features of patients with hypoglycemia with focal neurological signs (HFNS). Among 80 consecutive hypoglycemic patients (blood glucose levels less than 50mg/dL), who had been admitted between October 2008 and May 2012, we selected 11 patients (6 men and 5 women; mean age, 73.2 ± 12 years) with focal neurological signs. The mean initial blood glucose level was 27.9 mg/dL (range, 13-39 mg/dL). The most frequent symptom was unilateral motor weakness (n = 9), which was usually accompanied with mild or moderate alteration of consciousness. All patients had improved initial neurological signs within 1h of glucose injection. The initial DWI demonstrated a hyperintense lesion in the contralateral internal capsule with decreased values on the ADC (apparent diffusion coefficient) map in 2 of the patients (18%). The DWI performed one day later shows only faint lesion. The initial DWI in patients with HFNS may display a hyperintense lesion, which was difficult to distinguish from acute cerebral infarction. Hypoglycemia should be considered in cases with DWI showing a disproportionally small lesion in contrast to neurological signs.

Clinical and Neuroimaging Profile of Children with Lesions in the Corpus Callosum

PURPOSE

T2-hyperintense signal changes in corpus callosum (CC) have been described in epilepsy and encephalitis/encephalopathy. Little is known about their pathophysiology. The aim of this study was to examine the clinical presentation and evolution of CC lesions and relationship to seizures.

METHODS

We identified 12 children among 29,634 patients from Radiology Database. We evaluated following characteristics: seizures and accompanying medical history, antiepileptic drug usage, presenting symptoms, and radiological evolution of lesions.

RESULTS

CC lesions were seen in patients with prior diagnosis of epilepsy (n = 5) or in those with new onset seizures (n = 3), or with encephalitis/encephalopathy without history of seizures (n = 4). Seizure clustering or disturbances of consciousness were the main presenting symptoms. No relationship was observed between CC lesion and AEDs. On imaging, ovoid lesions at presentation resolved on follow up imaging and linear lesions persisted. DTI showed that the fibers passing through splenial lesions originated from the posterior parietal cortex and occipital cortex bilaterally.

CONCLUSION

In patients with seizures, no clear relationship was demonstrated between seizure characteristics or AED use with CC lesions. Ovoid lesions resolved and may have different pathophysiologic mechanism when compared to linear lesions that persisted.

Effect of hypoglycemia on brain structure in people with type 2 diabetes: epidemiological analysis of the ACCORD-MIND MRI trial

OBJECTIVE

The effect of hypoglycemia related to treatment of type 2 diabetes mellitus (T2DM) on brain structure remains unclear. We aimed to assess whether symptomatic severe hypoglycemia is associated with brain atrophy and/or white matter abnormalities.

RESEARCH DESIGN AND METHODS

We included T2DM participants with brain MRI from the Action to Control Cardiovascular Risk in Diabetes-Memory in Diabetes (ACCORD-MIND) trial. Symptomatic severe hypoglycemia was defined as blood glucose <2.8 mmol/L or symptoms resolved with treatments that required the assistance of another person or medical assistance (hypoglycemia requiring assistance [HA]). Standardized brain MRI was performed at baseline and at 40 months. Total brain volume (TBV) and abnormal white matter (AWM) volume were calculated using an automated computer algorithm. Brain MRI scans of hypoglycemic participants were also reviewed for local disease.

RESULTS

Of the 503 T2DM participants (mean age, 62 years) with successful baseline and 40-month brain MRI, 28 had at least one HA episode during the 40-month follow-up. Compared with participants without HA, those with HA had marginally significant less atrophy (less decrease in TBV) from baseline to 40 months (-9.55 [95% CI -15.21, -3.90] vs. -15.38 [95% CI -16.64, -14.12], P = 0.051), and no significant increase of AWM volume (2.06 [95% CI 1.71, 2.49] vs. 1.84 [95% CI 1.76, 1.91], P = 0.247). In addition, no unexpected local signal changes or volume loss were seen on hypoglycemic participants' brain MRI scans.

CONCLUSIONS

Our study suggests that hypoglycemia related to T2DM treatment may not accentuate brain pathology, specifically brain atrophy or white matter abnormalities.

Hypoglycaemia in diabetes mellitus: epidemiology and clinical implications

Hypoglycaemia is a frequent adverse effect of treatment of diabetes mellitus with insulin and sulphonylureas. Fear of hypoglycaemia alters self-management of diabetes mellitus and prevents optimal glycaemic control. Mild (self-treated) and severe (requiring help) hypoglycaemia episodes are more common in type 1 diabetes mellitus but people with insulin-treated type 2 diabetes mellitus are also exposed to frequent hypoglycaemic events, many of which occur during sleep. Hypoglycaemia can disrupt many everyday activities such as driving, work performance and leisure pursuits. In addition to accidents and physical injury, the morbidity of hypoglycaemia involves the cardiovascular and central nervous systems. Whereas coma and seizures are well-recognized neurological sequelae of hypoglycaemia, much interest is currently focused on the potential for hypoglycaemia to cause dangerous and life-threatening cardiac complications, such as arrhythmias and myocardial ischaemia, and whether recurrent severe hypoglycaemia can cause permanent cognitive impairment or promote cognitive decline and accelerate the onset of dementia in middle-aged and elderly people with diabetes mellitus. Prevention of hypoglycaemia is an important part of diabetes mellitus management and strategies include patient education, glucose monitoring, appropriate adjustment of diet and medications in relation to everyday circumstances including physical exercise, and the application of new technologies such as real-time continuous glucose monitoring, modified insulin pumps and the artificial pancreas.

MR screening of candidates for thrombolysis: How to identify stroke mimics?

Stroke mimics account for up to a third of suspected strokes. The main causes are epileptic deficit, migraine aura, hypoglycemia, and functional disorders. Accurate recognition of stroke mimics is important for adequate identification of candidates for thrombolysis. This decreases the number of unnecessary treatments and invasive vascular investigations. Correctly identifying the cause of symptoms also avoids delaying proper care. Therefore, this pictorial review focuses on what the radiologist should know about the most common MRI patterns of stroke mimics in the first hours after onset of symptoms. The issues linked to the accurate diagnosis of stroke mimics in the management of candidates for thrombolysis will be discussed.

Neuroimaging correlates of acute encephalopathy

Acute encephalopathies arise as a result of various contributions from infections or toxic, metabolic, and/or structural cerebral derangements. With the variety of clinical presentations, neurologic examination, electroencephalography (EEG), and imaging may not identify specific etiologies, but in combination, they can offer guidance regarding underlying causes. Among several different neuroimaging techniques, cerebral computed tomography and brain magnetic resonance imaging are most frequently used for diagnosis, treatment monitoring, and prognostication in acute brain dysfunction. This review compiles the most common and typical features of head computed tomography and magnetic resonance imaging and presents the clinical and EEG associations in adult patients with different types of acute encephalopathy.

Hyperacute ischemic stroke without lesions on diffusion-weighted imaging in a patient treated with rtPA thrombolysis

Key Clinical Message

We report a comatose patient with severe neurological deficits who was without spontaneous language or movement. He had a good response to recombinant tissue plasminogen activator (rtPA) thrombolysis even though there were no detectable lesions on diffusion-weighted imaging (DWI). DWI is very sensitive for diagnosing hyperacute ischemic stroke, and rtPA thrombolysis is the best treatment. However, rtPA thrombolysis in ischemic stroke patients without lesions on DWI has rarely been reported.

Hypoglycemia-induced spontaneous unilateral jerking movement in bilateral internal capsule posterior limb abnormalities

We report an 89-year-old woman who developed consciousness disturbance associated with marked hypoglycemia, and showed involuntary movements manifested as spontaneous quick-jerking flexion followed by slow relaxation, in the right leg. Diffusion-weighted imaging revealed bilateral hyperintensities in the posterior limbs of the internal capsule (P-IC). She was treated with intravenous glucose supplementation, and her symptoms dramatically improved. The P-IC lesions are common abnormalities on MRI in hypoglycemia, and may cause paralysis. However involuntary movements associated with the lesions are rarely observed. The spontaneous jerking movements observed in this patient might result from transient impairment of the pyramidal tract associated with hypoglycemia.

Transient interhemispheric disconnection in a case of insulinoma-induced hypoglycemic encephalopathy

We report a case of a 22-year-old male who was transferred to our hospital in a comatose state following successive seizures. Low blood glucose had been detected upon his arrival at the previous hospital. He became responsive 12 days after the onset of coma. Upon regaining consciousness he exhibited severe dysarthria and several interhemispheric disconnection signs such as intermanual conflict, left-hand dysgraphia, left hemispatial neglect confined to the right hand, impaired interhemispheric transfer, and unilateral constructional apraxia of the right hand. Brain MRI disclosed T2-weighted and diffusion-weighted hyperintense lesions with reduced apparent diffusion coefficients in the bilateral centrum semiovale, splenium of the corpus callosum, right posterior limb of the internal capsule, and bilateral middle cerebellar peduncles. As the MRI findings vanished, his interhemispheric disconnection signs gradually resolved. Abdominal imaging studies revealed a pancreatic tumor, which was later endocrinologically diagnosed as an insulinoma. This is an extremely rare report of interhemispheric disconnection signs due to hypoglycemic encephalopathy. The lesions in the bilateral centrum semiovale likely contributed to the interhemispheric disconnection signs.

Neuroimaging in patients with abnormal blood glucose levels

SUMMARY

Smooth neuronal functioning requires an uninterrupted supply of energy that is provided by glucose under normal physiologic conditions. Significant variations in plasma glucose levels, be it hypoglycemia or hyperglycemia, can present with myriad clinical manifestations and may mimic stroke. At times, the diagnosis is either not apparent or not clinically suspected. Imaging can suggest the diagnosis in unsuspected cases and can help in the assessment of the extent of neuronal damage in known cases, making it vital for the neuroradiologist to be aware of both common and atypical neuroimaging findings in hypoglycemia and hyperglycemia.

Hypoglycaemic episodes and risk of dementia in diabetes mellitus: 7-year follow-up study

OBJECTIVE

We investigated the risk of dementia in patients with type 2 diabetes with or without prior hypoglycaemic episodes.

SUBJECTS AND SETTING

One million subjects randomly selected from the National Health Insurance Research Database, Taiwan.

RESULTS

A total of 15 404 diabetic subjects without prior dementia and a mean age of 64.2 years were enrolled in the study. About 2% (n = 289) of participants had at least one episode of hypoglycaemia in a 3-year period; these subjects were older and more likely to be women and also had higher rates of insulin use and comorbidities compared to those without hypoglycaemia. During a total of 7 years of follow-up (mean and median follow-up, 3.8 and 4.8 years, respectively), 1106 patients with diabetes (7.2%) developed dementia. The incidence rate of dementia was higher in diabetic subjects with [29.9 per 1000 person-years (95% CI 22.1-39.2)] compared to those without [11.1 per 1000 person-years (95% CI 10.3-11.8)] hypoglycaemic episodes. The crude rate ratio (RR) and age- and gender-adjusted RR values for dementia were 2.76 (95% CI 2.06-3.70, P < 0.001) and 1.60 (95% CI 1.19-2.14, P = 0.002), respectively, in diabetic subjects with hypoglycaemia compared to those without hypoglycaemia. Results of Cox proportional hazards analysis revealed that hypoglycaemia, older age, female gender and insulin use were independent predictors of dementia.

CONCLUSION

Adult diabetic patients with prior hypoglycaemia had a significantly increased risk of dementia. The influence of hypoglycaemic episodes on brain function warrants further investigation.

Acute symptomatic hypoglycaemia mimicking ischaemic stroke on imaging: a systemic review

BACKGROUND

Acute symptomatic hypoglycaemia is a differential diagnosis in patients presenting with stroke-like neurological impairment, but few textbooks describe the full brain imaging appearances. We systematically reviewed the literature to identify how often hypoglycaemia may mimic ischaemic stroke on imaging, common patterns and relationships with hypoglycaemia severity, duration, clinical outcome and add two new cases.

METHODS

We searched EMBASE and Medline databases for papers reporting imaging in adults with symptomatic hypoglycaemia. We analysed the clinical presentation, outcome, brain imaging findings, duration and severity of hypoglycaemia, time course of lesion appearance, including two new cases.

RESULTS

We found 42 papers describing computed tomography or magnetic resonance imaging in 65 patients, plus our two cases with symptomatic hypoglycaemia. Imaging abnormalities on computed tomography and magnetic resonance were uni or bilateral, cortical or sub-cortical. Thirteen (20%) mimicked cortical or lacunar stroke. Acute lesions had restricted diffusion on magnetic resonance or low attenuation on computed tomography, plus swelling; older lesions showed focal atrophy or disappeared, as with ischaemic stroke. The association between the depth or duration of hypoglycaemia, the severity or extent of neurological deficit, and the imaging abnormalities, was weak.

CONCLUSION

Imaging abnormalities in patients with hypoglycaemia are uncommon but very variable, weakly associated with neurological deficit, and about a fifth mimic acute ischaemic stroke. Blood glucose testing should be routine in all patients with acute neurological impairment and hypoglycaemia should be included in the differential diagnosis of imaging appearances in patients presenting with acute stroke.

Acute mitochondrial encephalopathy reflects neuronal energy failure irrespective of which genome the genetic defect affects

Mitochondrial dysfunction and disease may arise as a result of mutations in either the mitochondrial genome itself or nuclear encoded genes involved in mitochondrial homeostasis and function. Irrespective of which genome is affected, mitochondrial encephalopathies share clinical and biochemical features suggesting common pathophysiological pathways. Two common paradigms of mitochondrial encephalopathy are mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes caused by maternally transmitted mutations of mitochondrial DNA and mitochondrial spinocerebellar ataxia and epilepsy caused by recessively inherited mutations of the nuclear-encoded DNA polymerase gamma, which replicates and repairs the mitochondrial genome. We studied and compared the disease mechanisms involved in these two syndromes. Despite having different genetic origins, their pathophysiological pathways converge on one critical event, damage to the respiratory chain leading to insufficient energy to maintain cellular homeostasis. In the central nervous system, this appears to cause selective neuronal damage leading to the development of lesions that mimic ischaemic damage, but which lack evidence of decreased tissue perfusion. Although these stroke-like lesions may expand or regress dynamically, the critical factor that dictates prognosis is the presence of epilepsy. Epileptic seizures increase the energy requirements of the metabolically already compromised neurons establishing a vicious cycle resulting in worsening energy failure and neuronal death. We believe that it is this cycle of events that determines outcome and which provides us with a mechanistic structure to understand the pathophysiology of acute mitochondrial encephalopathies and plan future treatments.

A case of hypoglycemic hemiparesis and literature review

An 89-year-old man with diabetes treated with metformin 500 mg/day and glimepiride 4 mg/day was hospitalized because of hypoglycemic right hemiparesis and dysarthria (casual glucose value 1.8 mmol/L), which resolved quickly following administration of 40 mL of 40% dextrose. Hemiparesis is a rare symptom (4.2%) of hypoglycemia. There are about 200 case reports of hypoglycemic hemiparesis. The average glucose level at which hemiparesis developed was 1.8 mmol/L. Right-sided hemiparesis predominated (R 66%; L 34%). On imaging studies, abnormal findings were frequently observed in the internal capsule or splenium of the corpus callosum. The mechanism of hemiparesis is not fully understood. The existence of cases in which hypoglycemia cannot be distinguished from stroke on imaging studies suggests the importance of measurement of the blood glucose level when the symptoms of stroke are first recognized.

Hypoglycemic encephalopathy: a case series and literature review on outcome determination

Data on clinical long-term outcome after the acute phase of hypoglycemic encephalopathy (HE) using validated outcome scales is currently unavailable. Here we report the results of a systematic literature search for studies on HE and data on long-term outcome in patients with HE admitted to three Charité hospitals between January 2005 and July 2010. HE was defined as coma/stupor and blood glucose levels <50 mg/dl on admission, persistence of coma/stupor for ≥24 h despite normalization of blood glucose levels, and exclusion of any other cause of coma/stupor. Outcome was assessed using the modified Rankin scale (mRS), Glasgow Outcome Scale (GOS), and Barthel index (BI). Fifteen patients were included, with a mean age of 60 years (range 29-79). Two were lost to follow-up. Of the remaining 13 patients, six had died (46 %). In the seven survivors, the median mRS score was 0 (range 0-5), median GOS score was 5 (range 2-5), and median BI was 100 (range 0-100). MRIs made in the acute phase were available for three patients and revealed no obvious relation between lesion size or pattern and clinical outcome. To our knowledge, this is the first case series using validated clinical scoring systems to determine clinical long-term outcome after HE. The results suggest that mortality is high, but long-term survival with little or no disability is possible and can be observed in the majority of survivors. Risk of death or poor outcome does not seem to be related to MRI features in the acute phase but rather to other presumably medical factors.

Metabolic encephalopathies

Kinnier Wilson coined the term metabolic encephalopathy to describe a clinical state of global cerebral dysfunction induced by systemic stress that can vary in clinical presentation from mild executive dysfunction to deep coma with decerebrate posturing; the causes are numerous. Some mechanisms by which cerebral dysfunction occurs in metabolic encephalopathies include focal or global cerebral edema, alterations in transmitter function, the accumulation of uncleared toxic metabolites, postcapillary venule vasogenic edema, and energy failure. This article focuses on common causes of metabolic encephalopathy, and reviews common causes, clinical presentations and, where relevant, management.

Early diffusion MR imaging findings and short-term outcome in comatose patients with hypoglycemia

BACKGROUND AND PURPOSE

The relationship between the MR imaging features and clinical outcomes in patients with hypoglycemic encephalopathy has always been evaluated retrospectively. The aim of this study was to prospectively evaluate whether MR imaging features of patients presenting with hypoglycemic coma are predictive of short-term (1-week) outcomes.

MATERIALS AND METHODS

Subjects were 36 consecutive patients with hypoglycemia who were in a comatose state on arrival at our hospital from April 2006 to March 2010. MR imaging findings on arrival in relation to the patients' clinical course after glucose infusion were evaluated.

RESULTS

Thirteen of the 36 patients showed no MR imaging abnormalities on arrival. DWI revealed focal lesions involving the internal capsule in 13 patients and lesions involving bilateral hemispheric white matter in 10 patients. After glucose administration, the patients without lesions and patients with focal internal capsule lesions recovered completely within 1 day. However, patients with diffuse white matter lesions did not recover even within 1 week despite glucose administration. There was no statistical difference in the initial blood glucose levels among patients with the various types of MR imaging findings.

CONCLUSIONS

On early MR imaging, hypoglycemic brain injury may first appear in the internal capsule and then spread into the hemispheric white matter. The absence of a lesion or the presence of a focal internal capsule lesion may suggest a good outcome. However, diffuse hemispheric white matter lesions may indicate a poor 1-week outcome.

A case of reversible splenial lesions in late postpartum preeclampsia

There have been reports of various etiologies associated with reversible splenial lesions manifested as obviously restricted diffusion. We describe for a 27-year-old woman suffering from late postpartum preeclampsia associated with reversible splenial lesions. This association has not been reported to date. Awareness that profound late postpartum preeclampsia can rarely result in abnormalities of the splenium of the corpus callosum (SCC) may help clinicians avoid unnecessary diagnostic procedures and therapeutic interventions. Moreover, it must be stated that prediction of the clinical course based on DWI and ADC values should be used with caution.

Serum calcium concentration affects signal changes on diffusion-weighted imaging in hypoglycemic encephalopathy

BACKGROUND AND PURPOSE

Abnormal signals in brain DWI may appear in patients with HE. The aim of this study was to compare the clinical condition and various physiologic factors between patients with HE with and without abnormal signal intensity changes on DWI.

MATERIALS AND METHODS

We retrospectively enrolled patients with HE who underwent brain DWI studies from January 2002 to November 2010. A diagnosis of HE was defined as low serum glucose levels (<50 mg/dL) with alteration of consciousness. Several clinical conditions and physiologic parameters were compared between patients with and without abnormal signals on DWI, including consciousness levels; outcome; body temperature; blood pressure; and serum levels of glucose, calcium, sodium, blood urea nitrogen, and creatinine.

RESULTS

Nine patients with HE were included, and 3 of them (33%) had abnormal signals on brain DWI. There was a trend toward serum calcium concentrations being lower in patients with normal findings on DWI studies compared with patients with abnormal DWI signals (7.6 ± 1.7 versus 9.4 ± 0.7 mg/dL, P = .07). Serum glucose concentration, duration of hypoglycemia, consciousness levels, other physiologic parameters, and clinical outcome did not reveal any differences between the 2 groups.

CONCLUSIONS

One-third of patients with HE had abnormal signals on brain DWI, and patients with low serum calcium levels may be less likely to present with abnormal DWI signals.

Diffusion-weighted imaging of hyperacute cerebral hypoglycemia

BACKGROUND AND PURPOSE

Cerebral hypoglycemia can result in reversible metabolic brain insults and can be associated with impaired diffusion disturbances. Our aim was to evaluate possible changes in DWI of the human brain during hyperacute short-term severe hypoglycemia.

MATERIALS AND METHODS

Ten individuals scheduled for a clinical IST were examined with DWI while the test was performed. Venous blood glucose was continuously measured, and sequential DWI sequences were performed without interruption. Hypoglycemia was terminated with intravenous glucose administration when glucose levels were at ≤2.0 mmol/L.

RESULTS

Blood glucose levels were lowered to a mean nadir of 1.75 ± 0.38 mmol/L. No alterations of cerebral diffusion could be observed in any individuals on DWI.

CONCLUSIONS

Hyperacute short-term severe hypoglycemia does not induce visible changes in DWI of the human brain.

Isolated reversible splenial lesion in tick-borne encephalitis: a case report and literature review

Here, we demonstrate a first case of tick-borne encephalitis (TBE) associated with an isolated reversible splenial corpus callosum lesion (IRSL) and highlight the wide range of different clinical entities in which such alterations have been observed. A 42-year-old man showed fever, cephalgia and mild disturbance of coordination and gait. Diagnosis was ascertained by slight CSF-pleiocytosis and positive TBE-IgG as well as by positive intrathekal specific antibody index on follow-up. MRI demonstrated a single ovoid hyperintensity in T2 and DWI with reduction in ADC in the splenium of corpus callosum which was abrogated in follow-up after 6 weeks. Most entities of IRSL presented with excellent prognosis, including our novel case of TBE. We discuss different possible pathomechanisms and the so far unexplained propensity of the splenium for such alterations. Clinicians should be familiar with this phenomenon to avoid unnecessary diagnostic or therapeutic efforts.

Seizures: emergency neuroimaging

The various findings observed on computed tomography (CT) and magnetic resonance (MR) imaging examinations in patients with seizures reflect the variety of different causes that give rise to this common neurologic symptom. In the emergency setting, CT is most valuable in its ability to accurately identify acute abnormalities that require emergent medical or surgical treatment. MR imaging, by contrast, is usually reserved for patients with recurrent or refractory seizures. The accurate interpretation of either modality requires familiarity with how seizures are classified clinically, the most common presenting features of different causes for seizures, the relevant neuroanatomy, and the imaging manifestations of both common and uncommon causes of seizures and epilepsy. Of particular practical importance to the radiologist is the ability to recognize (1) the most common findings in patients with recurrent seizures and (2) potentially reversible causes for seizures that require prompt intervention to avoid or minimize permanent brain injury. This article surveys a variety of different causes for seizures and epilepsy, focusing on specific clinical features that can help to refine differential diagnosis, and on imaging findings characteristic of different disorders.

Localized cerebral energy failure in DNA polymerase gamma-associated encephalopathy syndromes

Mutations in the catalytic subunit of the mitochondrial DNA-polymerase gamma cause a wide spectrum of clinical disease ranging from infantile hepato-encephalopathy to juvenile/adult-onset spinocerebellar ataxia and late onset progressive external ophthalmoplegia. Several of these syndromes are associated with an encephalopathy that characteristically shows episodes of rapid neurological deterioration and the development of acute cerebral lesions. The purpose of this study was to investigate the nature, distribution and natural evolution of central nervous system lesions in polymerase gamma associated encephalopathy focusing particularly on lesions identified by magnetic resonance imaging. We compared radiological, electrophysiological and pathological findings where available to study potential mechanisms underlying the episodes of exacerbation and acute cerebral lesions. We studied a total of 112 magnetic resonance tomographies and 11 computed tomographies in 32 patients with polymerase gamma-encephalopathy, including multiple serial examinations performed during both the chronic and acute phases of the disease and, in several cases, magnetic resonance spectroscopy and serial diffusion weighted studies. Data from imaging, electroencephalography and post-mortem examination were compared in order to study the underlying disease process. Our findings show that magnetic resonance imaging in polymerase gamma-related encephalopathies has high sensitivity and can identify patterns that are specific for individual syndromes. One form of chronic polymerase gamma-encephalopathy, that is associated with the c.1399G > A and c.2243G > C mutations, is characterized by progressive cerebral and cerebellar atrophy and focal lesions of the thalamus, deep cerebellar structures and medulla oblongata. Acute encephalopathies, both infantile and later onset, show similar pictures with cortical stroke-like lesions occurring during episodes of exacerbation. These lesions can occur both with and without electroencephalographic evidence of concurrent epileptic activity, and have diffusion, spectroscopic and histological profiles strongly suggestive of neuronal energy failure. We suggest therefore that both infantile and later onset polymerase gamma related encephalopathies are part of a continuum.

Diffusion MR imaging of hypoglycemic encephalopathy

BACKGROUND AND PURPOSE

MR imaging features of HE have not been fully established. The purpose of this study was to determine the topographic distribution and DWI findings of HE.

MATERIALS AND METHODS

We retrospectively evaluated HE MR imaging (n = 11). The topographic distribution of the lesions was evaluated on routine MR imaging, and DWI SI and ADC values were assessed. The ADC value of involved lesions was compared with the noninvolved subcortical WM area by use of the paired t test.

RESULTS

MR images demonstrated bilateral diffusion-restrictive lesions in the posterior limb of the IC (n = 6), cerebral cortex (n = 8), CR (n = 7), CS (n = 9), hippocampus (n = 4), and BG (n = 1). The mean ADC value of lesions was 448.82 +/- 92.34 x 10(-6) mm(2)/s compared with the mean ADC value of noninvolved lesions (837.72 +/- 62.14 x 10(-6) mm(2)/s); this difference was statistically significant (P < .000). The lesions showed complete resolution on follow-up DWI for 6 patients. Three patients with cortical involvement of > or = 2 lobes showed partial recovery or death, but most of the other patients with WM involvement or cortical involvement in only 1 lobe experienced complete recovery.

CONCLUSIONS

The topographic localization of the lesions was the posterior limb of the IC, cerebral cortex, CR, CS, hippocampus, and BG. Most HE lesions probably correspond to areas of reversible cytotoxic edema as seen on DWI, which can predict the prognosis of HE according to the degree of lesion extent.

Rapid improvement of diffusion-weighted imaging abnormalities after glucose infusion in hypoglycaemic coma

Diffusion-weighted imaging (DWI) may detect hyperintense lesions in patients with transient hypoglycaemia-induced hemiparesis or coma, which are completely reversible after glucose infusion.1(-)3 In vivo animal studies have documented the visualisation of such hypoglycaemia-induced changes of signal intensity and the reversal by glucose intake in detail.4 However, the time necessary for hyperintense lesions on DWI to disappear after glucose infusion in humans is still unclear. A 54 year old woman presented comatose with brain stem signs and severe hypoglycaemia. DWI demonstrated hyperintense lesions in the corpus callosum and internal capsules. She was treated with IV glucose. These lesions had resolved significantly on imaging 2 hours later and completely resolved on repeat imaging 2 days later. This report documents the time course of recovery of neurological lesions induced by hypoglycaemia after treatment with IV glucose.

Severe hypoglycemia associated with an illegal sexual enhancement product adulterated with glibenclamide: MR imaging findings

PURPOSE

To describe the magnetic resonance (MR) imaging findings associated with severe hypoglycemia after consumption of an illegal sexual enhancement product (Power 1 Walnut) adulterated with glibenclamide, an oral hypoglycemic agent used to treat diabetes mellitus.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective study. Records in eight male patients with severe hypoglycemia of unknown cause, without prior treatment for diabetes, and with positive blood toxicology results for glibenclamide were reviewed. MR imaging included diffusion-weighted imaging and, in some patients, MR angiography, dynamic contrast material-enhanced perfusion MR imaging, and MR spectroscopy.

RESULTS

In seven patients, there were hyperintense abnormalities on diffusion-weighted and T2-weighted images in the hippocampus and cerebral cortex, sparing the subcortical white matter and cerebellum. Three patients had abnormalities of the splenium of the corpus callosum, and one had widespread involvement, including the caudate nucleus, basal ganglia, and internal capsule bilaterally. In three patients, unilateral cortical involvement, which did not conform to the typical cerebral arterial territories, was noted. In one patient, perfusion MR imaging showed slightly increased relative cerebral blood volume, and MR spectroscopy revealed no evidence of abnormal lactate in the affected cerebral cortex.

CONCLUSION

Diffusion-weighted MR imaging findings in patients with severe hypoglycemia showed typical lesions in the hippocampus and cerebral cortex, but the caudate nucleus and basal ganglia were involved in only the most severely affected patient. The splenium of the corpus callosum and internal capsule were also abnormal in three patients, and unilateral cortical lesions could be distinguished from acute ischemic stroke by the pattern of involvement and MR angiographic, perfusion, and spectroscopic findings.

Levofloxacin-associated hypoglycaemia complicated by pontine myelinolysis and quadriplegia

BACKGROUND

Central pontine myelinolysis (CPM) usually presents in chronic alcoholics and in patients in whom hyponatraemia has been corrected rapidly. However, CPM may occur in other clinical circumstances, including patients with severe hypoglycaemia. We describe the occurrence of CPM and quadriplegia in a patient who experienced fluoroquinolone-associated severe hypoglycaemia.

CASE REPORT

A 63-year-old man with Type 2 diabetes mellitus was admitted to hospital for resection of a large liposarcoma. Renal-dose levofloxacin was utilized as part of an antimicrobial regimen to treat post-operative peritonitis. On days 6-8 of levofloxacin therapy, the patient experienced recurrent hypoglycaemia despite total parenteral nutrition, 10% dextrose containing fluids and cessation of insulin therapy 3 days prior to the first hypoglycaemic episode. Hypoglycaemia resolved within 24 h of stopping levofloxacin. After a final and severe hypoglycaemic event, the patient developed quadriplegia and tonic left deviation of gaze. Magnetic resonance imaging revealed a high-intensity lesion in the central pons consistent with CPM.

CONCLUSIONS

Fluoroquinolones should be considered as a potential cause of hypoglycaemia. Severe hypoglycaemia has the potential to cause white matter lesions in the pons. Putative mechanisms include failure of membrane ion channels, oligodendrocyte apoptosis and oxidative stress of glucose reperfusion. Fluoroquinolone-associated hypoglycaemia and hypoglycaemia-induced quadriplegia are both rare and we believe this is the first case report linking the two events.

Clinical review: Prognostic value of magnetic resonance imaging in acute brain injury and coma

Progress in management of critically ill neurological patients has led to improved survival rates. However, severe residual neurological impairment, such as persistent coma, occurs in some survivors. This raises concerns about whether it is ethically appropriate to apply aggressive care routinely, which is also associated with burdensome long-term management costs. Adapting the management approach based on long-term neurological prognosis represents a major challenge to intensive care. Magnetic resonance imaging (MRI) can show brain lesions that are not visible by computed tomography, including early cytotoxic oedema after ischaemic stroke, diffuse axonal injury after traumatic brain injury and cortical laminar necrosis after cardiac arrest. Thus, MRI increases the accuracy of neurological diagnosis in critically ill patients. In addition, there is some evidence that MRI may have potential in terms of predicting outcome. Following a brief description of the sequences used, this review focuses on the prognostic value of MRI in patients with traumatic brain injury, anoxic/hypoxic encephalopathy and stroke. Finally, the roles played by the main anatomical structures involved in arousal and awareness are discussed and avenues for future research suggested.

Imaging of the brain in children with type I diabetes mellitus

Type 1 diabetes mellitus (DM) affects about 1 in 500 children and can cause damage to multiple organ systems. In recent years, growing attention has been given to the effects of type 1 DM on the brain. In this article we review important imaging features of the brain in children with type 1 DM, including (1) imaging the child in diabetic ketoacidosis and the child with hypoglycemia, (2) syndromes associated with type 1 DM, and (3) long-term effects of type 1 DM on brain structure.