Activation of epileptogenic foci by hyperosmolality

Electroencephalography of encephalopathy in patients with endocrine and metabolic disorders

Patients with acute alteration in mental status from encephalopathy because of underlying metabolic-toxic or endocrine abnormalities are frequently seen in the acute hospital setting. A rapid diagnosis and correction of the underlying cause is essential as a prolonged state of encephalopathy portends a poor outcome. Correct diagnosis and management remain challenging because several encephalopathies may present similarly, and further laboratory, imaging, or other testing may not always reveal the underlying cause. EEG provides rapid additional information on the encephalopathic patient. It may help establish the diagnosis and is indispensable for identifying nonconvulsive status epilepticus, an important possible complication in this context. The EEG may assist the clinician in gauging the severity of brain dysfunction and may aid in predicting outcome. This review summarizes the current knowledge on EEG findings in selected metabolic and endocrine causes of encephalopathy and highlights distinct EEG features associated with particular etiologies.

Clinical characteristics, etiology and long-term outcome of epilepsia partialis continua in adult patients in Thailand

OBJECTIVE

Epilepsia partialis continua (EPC) is clinically defined as a syndrome of continuous focal jerking of a body part. EPC has various etiologies and outcomes depending on its cause. Most studies on EPC have been conducted in Western countries and no study on the long-term outcome in adult onset epilepsia partialis continua has been reported. The aim of this study was to analyze the clinical characteristics, etiology, and treatment outcome and measurement to identify conditions that are predictive of long-term excellent outcome following epilepsia partialis continua in Thailand.

METHODS

Our study was characterized by a retrospective systematic data collection between 2003 and 2010 that lead to the inclusion of a total of 75 patients, with epilepsia partialis continua at Songklanagarind Hospital, Thailand. All of the patients received brain CT scans or MRIs after diagnosis with EPC. Basic laboratory investigations including blood sugar, blood urea nitrogen, creatinine, electrolyte, calcium, liver function, and complete blood count tests were performed. Additionally, routine electroencephalography were performed and antiepileptic drugs were given to all patients. Therapeutic outcomes and the degree of seizure control after discharge were determined by the functional status and Seizure Frequency Scoring Systems, respectively.

KEY FINDING

All of our patients manifested as motor EPC. The mean duration of EPC was 6.2 days (range 1-30 days) and the most frequent distribution of EPC involved the face and arms (42.7%). Hyperglycemia was the most common cause of EPC (34 patients, 45.3%). Fifty-one patients had an excellent outcome and 24 patients had a non-excellent outcome. All of the patients with hyperglycemia had an excellent outcome and required no antiepileptics in the long term. Predictors of excellent outcome in the scoring system for seizure frequency were metabolic or hyperglycemia-induced EPC, monotherapy and duration of EPC.

SIGNIFICANCE

The characteristics of epilepsia partialis continua in this study were different from those of EPC in Western countries. Its most common cause was hyperglycemia and prognostic factors depended on etiology, number of AEDs, and duration of EPC.

Visual hallucination of coloured numbers secondary to hyperglycaemia

A 70-year-old Indian woman presented with confusion and visual hallucinations of brightly coloured numbers slowly roving across the right visual field. These hallucinations occurred for a few minutes every few hours. Examination revealed a right homonymous hemianopia. Blood sugar was 37 mmol/l. EEG identified left occipital seizure activity. There was clinical and electrophysiological resolution with normalisation of the hyperglycaemia. There are few cases of hyperglycaemia associated with positive visual phenomena and hemianopia in the literature and this is the first case reported presenting with numerical hallucinations. Hyperglycaemia must be kept on a differential diagnosis list of unusual visual phenomena as it is easily correctable.

Complex partial seizures and aphasia as initial manifestations of non-ketotic hyperglycemia. Case report

We describe a case of non-ketotic hyperglycemia (NKH), heralded by complex partial seizures and aphasia of epileptic origin, besides versive and partial motor seizures. This clinical picture was accompanied by left fronto-temporal spikes in the EEG. The seizures were controlled by carbamazepine only after the control of the diabetes. A month later, carbamazepine was discontinued. The patient remained without seizures, with normal language, using only glybenclamide. Complex partial seizures, opposed to simple partial seizures, are rarely described in association to NKH. Epileptic activity localized over language regions can manifest as aphasia.

[Partial motor seizures induced by movement in diabetic patients]

Three elderly patients with partial motor seizures triggered by movement of posture of an extremity are presented. They had a history of diabetes mellitus. Two of them had nonketotic hyperglycemia. Hemiparesis was present in the three patients, which resolved in two. In the other patient, hemiparesis resulted from a previous stroke. All patients had transitory parietal syndrome. During seizures, EEG showed discharges in the parieto-occipital area in two cases and in the mid-temporal area in one. Seizures were resistant to conventional anticonvulsant therapy, and ceased only after treatment of metabolic disturbances. A search for reflex seizures and hyperglycemia should be carried out routinely in the elderly with repeated spontaneous focal motor seizures. This may be important for treatment and prognosis.

Gaze-evoked visual seizures in nonketotic hyperglycemia

Focal motor seizures are commonly a symptom of nonketotic hyperglycemia (NKH). Posture-induced motor seizures are less common but have been reported in some patients with this disorder. We report the first case of gaze-evoked sensory (visual) seizures in nonketotic hyperglycemia. Both seizures and ictal EEG findings disappeared shortly after hyperglycemia was corrected.

Hyperglycemia presenting with occipital seizures

Seizures are common in hyperglycemia and are often the first manifestation, particularly in nonketotic hyperglycemia (NKH). Published reports emphasize partial motor seizures almost exclusively. In a 3-year period, we observed three patients in whom occipital seizures, documented by ictal EEG recording, were the initial symptom of hyperglycemia. One patient was mildly ketotic at first. Seizures were visual in two patients and visual and adversive in the third. Seizures regressed with correction of abnormal glucose levels and did not recur during follow-up of less than or equal to 1 year despite discontinuation of antiepileptic drugs (AEDs) in two. Computed tomography (CT) scans did not show correlative abnormalities. Although published reports suggest that frontal lobe structures are particularly susceptible to the epileptogenic effects of NKH, our experience indicates that in NKH epileptic foci may originate in other cortical areas, such as occipital.

Alterations of GABA metabolism and seizure susceptibility in the substantia nigra of the kindled rat acclimating to changes in osmotic state

Seizure susceptibility and GABA metabolism were altered in the substantia nigra [SN] of adult male Sprague Dawley rats when these animals were acclimating to an altered plasma osmolality. Changes in GABA metabolism were measured in vivo in SN of the freely moving rat. Suitable precautions were taken to avoid any post-mortem flux of glutamate to GABA and to correct for the underestimation of GABA build up in SN due to the finite diffusion rate of gamma-vinyl GABA [GVG] after stereotaxic injection of small amounts into one side of the brain. Control experiments provided evidence that changes in osmolality, within a normal physiological range, did not affect significantly gamma-aminobutyric acid transaminase [GABA-T]. Also kindling via the medial septum [MS], in the absence of electrical stimulation did not alter GABA metabolism in SN, thus providing a stable baseline for studies of osmotic effects. Hyperosmolality was associated with a rise in seizure thresholds, with a marked reduction of the rate of GABA synthesis in SN, and with a substantial increase in turnover time of the GABA pool. Hypoosmolality, of a degree known to be associated with mild cerebral edema and swelling localized to astrocytes, markedly reduced seizure threshold, and reduced GABA pool size in SN, but did not alter the rate of GABA synthesis significantly. These results demonstrate by new and independent means the relationship between GABA metabolism in the SN and seizure susceptibility in vivo.

Seizure and acute osmotic change: clinical and neurophysiological aspects

There are a number of clinical situations where overhydration may occur. If the reduction in plasma osmolality is acute, passive water influx swells brain cells, shrinking the extracellular space around them. It is during this time that susceptibility to generalized tonic-clonic seizure dramatically increases. Common clinical examples include hastened rehydration therapy, the dialysis disequilibrium syndrome, compulsive polydipsia, the syndrome of inappropriate ADH secretion (SIADH) and post-TURP syndrome. Treatments that tend to restore normal cellular volume (dehydration, mannitol infusion) help protect against this form of seizure. Support for a correlation between plasma osmolality and seizure susceptibility is scattered amongst the literature of several medical disciplines and spans almost 70 years. However a cellular basis to explain how overhydration might promote epileptiform activity has been examined only recently. The neocortical and hippocampal brain slice preparations permit an examination of how acute osmotic change alters cortical excitability independent of vascular damage, brain compression or other factors secondary to brain swelling. Electrophysiological evidence indicates that hyposmolality promotes epileptiform activity by strengthening both excitatory synaptic communication in neocortex and field effects among the entire cortical population. Moreover there is little evidence that associated hyponatremia in itself leads to increased CNS excitability. Such findings help in understanding how rapid lowering of plasma osmolality in clinical situations can promote the hyperexcitability associated with generalized tonic-clonic seizure.

Prolonged spontaneous complex visual hallucinations and illusions as ictal phenomena

A patient without a previous history of seizures had a generalized tonic-clonic seizure followed by multiple complex visual hallucinations and illusions (CVHIs) lasting weeks. The patient reported a total of 19 different CVHIs. EEGs performed revealed rhythmic right temporal activity occurring only during the CVHIs. Treatment with antiepileptic drugs (AEDs) resolved the CVHIs and normalized the EEG. An attempt at discontinuation of one AED resulted in a resurgence of the CVHIs and EEG abnormality.

Lingual seizures

A 73-year-old patient with hyperglycemia and rheumatoid arthritis presented with attacks of involuntary lingual movements that were associated with pain at the base of the tongue, often followed by aversion of head and eyes to the left with clonic contractions of the left corner of the mouth. Seizures could be induced by a combination of specific movement and somesthetic stimuli. Ictal EEG recording revealed a focal epileptiform discharge in the right centrofrontal area, thus confirming that the patient had lingual seizures, an extremely unusual manifestation.

Effect of altered blood plasma osmolalities on regional brain amino acid concentrations and focal seizure susceptibility in the rat

Blood plasma hypo- or hyperosmolality alters significantly the concentration of some amino acids in brain tissues of the medial septum and hippocampus of adult Sprague-Dawley rats. With some notable exceptions, brain amino acid concentrations decreased under hypoosmotic conditions and increased under hyperosmotic conditions. Osmotic changes and brain amino acid changes appear to be related to each other in an almost linear fashion. A comparison of rats and toads indicates that the patterns of changes in brain amino acid concentrations in response to a hypoosmotic plasma osmolality were almost identical for both species. Changes achievable under hyperosmotic conditions were considerably greater in toads. When rats with kindled epileptogenic foci were made hypoosmotic by water-loading, seizure thresholds decreased dramatically. Our data suggest a possible relationship between the hypoosmotically induced biochemical changes in brain tissues (especially some amino acid neurotransmitters and neurotransmitter precursors) and the hypoosmotically induced increase in seizure susceptibility.

Hyperosmolar hyperglycemic nonketotic syndrome. Report of 22 cases and brief review

In a series of 22 patients with the hyperosmolar hyperglycemic nonketotic syndrome managed during a five-year period in a community hospital setting, 21 patients were known to be diabetic and only six patients were in coma. The overall mortality was 36.3 percent, and seven of the eight deaths were explained by associated nonmetabolic causes. In this study, hyperosmolarity was not related to coma or to final outcome of treatment. Patients were managed with relatively small amounts of fluid, and the type of fluid used did not influence the final outcome.

Epilepsia partialis continua associated with nonketotic hyperglycemia: clinical and biochemical profile of 21 patients

In 21 patients, epilepsia partialis continua (EPC) was an early symptom of nonketotic hyperglycemia and occurred during an initial phase of hyponatremia and mild hyperosmolality. EPC persisted for an average of 8 days, and its duration correlated predominantly with the degree of hyponatremia. Depression of consciousness and cessation of seizures occurred with increasing severity of hyperglycemia and hyperosmolality. In 9 patients, EPC was the first symptom leading to the diagnosis of diabetes mellitus. Four patients died of serious associated illness. The majority of the patients had evidence of a localized structural cerebral lesion. Metabolic disturbances including hyperglycemia, mild hyperosmolality, hyponatremia, and lack of ketoacidosis contribute to the development of EPC in areas of focal cerebral damage.