Syndrome of alternating hypernatremia and hyponatremia after hypothalamic hamartoma surgery

OBJECT

In this paper, the authors' goal was to describe the occurrence of alternating hypernatremia and hyponatremia in pediatric patients who underwent resection of hypothalamic hamartomas (HHs) for epilepsy. Hypernatremia in patients after pituitary or hypothalamic surgery can be caused by diabetes insipidus (DI), whereas hyponatremia can occur due to a syndrome of inappropriate antidiuretic hormone, cerebral salt wasting, or excessive administration of desmopressin (DDAVP). The triphasic response after surgery in the pituitary region can also explain variations in sodium parameters in such cases.

METHODS

One hundred fifty-three patients with HH who underwent surgery were enrolled in a prospective study to monitor outcomes. Of these, 4 patients (2.6%) were noted to experience dramatic alterations in serum sodium values. The medical records of these patients were identified and evaluated.

RESULTS

Patients' ages at surgery ranged from 1.2 to 6.0 years. All patients were girls. Two patients had Delalande Type IV lesions (of 16 total Type IV lesions surgically treated) and 2 had Type III lesions (of 39 total Type III lesions). All patients had a history of gelastic seizures refractory to medication. Seizure frequency ranged from 3 to 300 per day. After surgery, all patients experienced hypernatremia and hyponatremia. The largest fluctuation in serum sodium concentration during hospitalization in a single patient was 53 mEq/L (range 123-176 mEq/L). The mean absolute difference in maximum and minimum sodium values was 38.2 mEq/L. All patients exhibited an initial period of immediate DI (independent of treatment) after surgery followed by a period of hyponatremia (independent of treatment), with a minimum value occurring between postoperative Days 5 and 8. All patients then returned to a hypernatremic state of DI, and 3 patients still require DDAVP for DI management. A second occurrence of hyponatremia lasting several days without DDAVP administration occurred in 2 patients during their hospitalization between periods of hypernatremia. One patient stabilized in the normal range of sodium values prior to discharge from rehabilitation without the need for further intervention. At last follow-up, 3 patients are seizure-free.

CONCLUSIONS

Severe instability of sodium homeostasis with hypernatremia and hyponatremia is seen in up to 2.6% of children undergoing open resection of HH. This risk appears to be related to HH type, with a higher risk for Types III (2 [5.1%] of 39) and IV (2 [12.5%] of 16) lesions. Here, the authors describe alternating episodes of hypernatremia and hyponatremia in the postoperative period following HH surgery. Management of this entity requires careful serial assessment of volume status and urine concentration and will often require alternating salt replacement therapy with DDAVP administration.

Functional rundown of gamma-aminobutyric acid(A) receptors in human hypothalamic hamartomas

OBJECTIVE

Human hypothalamic hamartomas (HHs) are highly associated with treatment-resistant gelastic seizures. HHs are intrinsically epileptogenic, although the basic cellular mechanisms responsible for seizure activity are unknown. Altered gamma-aminobutyric acid (GABA) function can contribute to epileptogenesis in humans and animal models. Recently, functional GABA(A) receptor (GABA(A) R) rundown has been described in surgically resected human temporal lobe epilepsy tissue. We asked whether functional GABA(A) R rundown also occurs in human HH neurons.

METHODS

GABA(A) R-mediated currents were measured using perforated patch-clamp recordings in single neurons acutely dissociated from surgically resected HH tissue. In addition, functional GABA(A) Rs were expressed in Xenopus oocytes after microinjection with membrane fractions from either HH or control hypothalamus, and were studied with 2-electrode voltage-clamp recordings.

RESULTS

Perforated patch-clamp recordings in dissociated HH neurons showed that repetitive exposure to GABA (5 consecutive exposures to 0.1 mM GABA with 1-second duration and at 20-second intervals) induced a time-dependent rundown of whole-cell currents in small HH neurons, whereas large HH neurons showed much less rundown using the same protocol. Functional rundown was not observed in HH neurons with repetitive exposure to glycine or glutamate. Two-electrode voltage-clamp recordings (6 consecutive exposures to 1 mM GABA with 10-second duration and at 40-second intervals) induced GABA current rundown in Xenopus oocytes microinjected with HH membrane proteins, but not in the oocytes expressing hypothalamic membrane proteins derived from human autopsy controls. Functional rundown of GABA currents was significantly attenuated by intracellular application of adenosine triphosphate or the nonspecific phosphatase inhibitor, okadaic acid.

INTERPRETATION

Neurons from surgically resected human HH demonstrate functional rundown of GABA(A) R-mediated transmembrane currents in response to GABA agonist exposure. Rundown may be a marker for impaired GABAergic function and a contributing mechanism for seizure genesis within HH tissue.

Ketogenic diet in the treatment of seizures associated with hypothalamic hamartomas

Seizures associated with hypothalamic hamartoma (HH) are notoriously intractable to medical therapy, and while surgical resection affords most affected patients with complete or near seizure-freedom, there remains a need to identify alternative treatments. In this retrospective study, we identified six patients from a large cohort of 220 patients with HH who were treated with the ketogenic diet (KD). Four patients had a 50-90% reduction in multiple seizure types (including gelastic, partial-onset and atonic seizures), and two individuals failed to respond. In order to study possible mechanisms, we then performed microelectrode recordings of small neurons in surgically resected HH tissue slices. Exposure to ketone bodies decreased spontaneous firing in 5 of 7 small HH neurons. These preliminary results suggest that seizures associated with HH may respond favorably to the KD, and that ketone bodies might directly modulate the intrinsic epileptogenicity of HH tissue.

L-Type calcium channel blockade reduces network activity in human epileptic hypothalamic hamartoma tissue

Purpose

Human hypothalamic hamartomas (HHs) are associated with gelastic seizures, intrinsically epileptogenic, and notoriously refractory to medical therapy. We previously reported that the L-type calcium channel antagonist nifedipine blocks spontaneous firing and γ-aminobutyric acid (GABA)_A–induced depolarization of single cells in HH tissue slices. In this study, we examined whether blocking L-type calcium channels attenuates emergent activity of HH neuronal networks.

Methods

A high-density multielectrode array was used to record extracellular signals from surgically resected HH tissue slices. High-frequency oscillations (HFOs, ripples and fast ripples), field potentials, and multiunit activity (MUA) were studied (1) under normal and provoked [4-aminopyridine (4-AP)] conditions; and (2) following nifedipine treatment.

Key Findings

Spontaneous activity occurred during normal artificial cerebrospinal fluid (aCSF) conditions. Nifedipine reduced the total number and duration of HFOs, abolished the association of HFOs with field potentials, and increased the inter-HFO burst intervals. Notably, the number of active regions was decreased by 45 ± 9% (mean ± SEM) after nifedipine treatment. When considering electrodes that detected activity, nifedipine increased MUA in 58% of electrodes and reduced the number of field potentials in 67% of electrodes. Provocation with 4-AP increased the number of events and, as the number of electrodes that detected activity increased 248 ± 62%, promoted tissue-wide propagation of activity. During provocation with 4-AP, nifedipine effectively reduced HFOs, the association of HFOs with field potentials, field potentials, MUA, and the number of active regions, and limited propagation.

Significance

This is the first study to report (1) the presence of HFOs in human subcortical epileptic brain tissue in vitro; (2) the modulation of “pathologic” high-frequency oscillations (i.e., fast ripples) in human epileptic tissue by L-type calcium channel blockers; and (3) the modulation of network physiology and synchrony of emergent activity in human epileptic tissue following blockade of L-type calcium channels. Attenuation of activity in HH tissue during normal and provoked conditions supports a potential therapeutic usefulness of L-type calcium channel blockers in epileptic patients with HH.

Surgical resection of hypothalamic hamartomas for severe behavioral symptoms

Hypothalamic hamartomas (HHs) are associated with treatment-resistant epilepsy. Many patients also experience severe and sometimes disabling psychiatric problems. The most common behavioral symptoms consist of paroxysms of uncontrolled anger related to poor frustration tolerance. These can include violence, resulting in disrupted family or school relationships, and legal consequences including incarceration. In a large cohort of patients undergoing surgical resection of HHs for refractory epilepsy, 88% of families described an improvement in overall behavioral functioning [1]. Here, we describe four patients (three males, mean age=11.9 years) who underwent surgical resection of HHs largely for behavioral indications. Three patients had relatively well controlled seizures, and one had no history of epilepsy. All patients had striking improvement in their psychiatric comorbidity. HH resection can result in significant improvement in behavioral functioning, even in patients with relatively infrequent seizures. Further investigation under approved human research protocols is warranted.

Gamma Knife surgery for hypothalamic hamartomas and epilepsy: patient selection and outcomes

Object

The authors present outcomes obtained in patients who underwent Gamma Knife surgery (GKS) at 1 institution as part of a multimodal treatment of refractory epilepsy caused by hypothalamic hamartomas (HHs).

Methods

Between 2003 and 2010, 19 patients with HH underwent GKS. Eight patients had follow-up for less than 1 year, and 1 patient was lost to follow-up. The 10 remaining patients (mean age 15.1 years, range 5.7–29.3 years) had a mean follow-up of 43 months (range 18–81 months) and are the focus of this report. Five patients had undergone a total of 6 prior surgeries: 1 transcallosal resection of the HH, 2 endoscopic transventricular resections of the HH, 2 temporal lobectomies, and 1 arachnoid cyst evacuation. In an institutional review board–approved study, postoperative complications and long-term outcome measures were monitored prospectively with the use of a proprietary database. Seven patients harbored Delalande Type II lesions; the remainder harbored Type III or IV lesions. Seizure frequency ranged from 1–2 monthly to as many as 100 gelastic seizures daily. The mean lesion volume was 695 mm3 (range 169–3000 mm3, median 265 mm3). The mean/median dose directed to the 50% isodose line was 18 Gy (range 16–20 Gy). The mean maximum point dose to the optic chiasm was 7.5 Gy (range 5–10 Gy). Three patients underwent additional resection 14.5, 21, and 32 months after GKS.

Results

Of the 10 patients included in this study, 6 are seizure free (2 after they underwent additional surgery), 1 has a 50%–90% reduction in seizure frequency, 2 have a 50% reduction in seizure frequency, and 1 has observed no change in seizure frequency. Overall quality of life, based on data obtained from follow-up telephone conversations and/or surveys, improved in 9 patients and was due to improvements in seizure control (9 patients), short-term memory loss (3 patients), and behavioral symptoms (5 patients); in 1 patient, quality of life remains minimally affected. Incidences of morbidity were all temporary and included poikilothermia (1 patient), increased depression (1 patient), weight gain/increased appetite (2 patients), and anxiety (1 patient) after GKS.

Conclusions

Of the approximately 150 patients at Barrow Neurological Institute who have undergone treatment for HH, the authors have reserved GKS for treatment of small HHs located distal from radiosensitive structures in patients with high cognitive function and a stable clinical picture, which allows time for the effects of radiosurgery to occur without further deterioration. The lack of significant morbidity and the clinical outcomes achieved in this study demonstrated a low risk of GKS for HH with results comparable to those of previous series.

Central precocious puberty due to hypothalamic hamartomas correlates with anatomic features but not with expression of GnRH, TGFalpha, or KISS1

BACKGROUND/AIMS

Hypothalamic hamartomas are the most common identifiable cause of central precocious puberty (CPP). Hamartoma characteristics proposed to be associated with CPP include specific anatomic features and expression of molecules such as gonadotropin-releasing hormone (GnRH), transforming growth factor alpha (TGFalpha), and GRM1A, which encodes the type 1 metabotropic glutamate receptor alpha isoform. We sought to determine whether hamartomas that cause CPP could be distinguished by anatomic features, expression of these molecules, or expression of KISS1, whose products signal through the receptor GPR54 to stimulate GnRH release.

METHODS

Clinical records and radiologic images were reviewed for 18 patients who underwent hamartoma resection for intractable seizures; 7 had precocious puberty. Resected tissue was examined for expression of GnRH, GnRH receptor (GnRHR), TGFalpha, KISS1, GPR54, and GRM1A.

RESULTS

Hypothalamic hamartomas associated with CPP were more likely to contact the infundibulum or tuber cinereum and were larger than hamartomas not associated with CPP. GnRH, TGFalpha, and GnRHR were expressed by all hamartomas studied. Expression of KISS1, GPR54, and GRM1A did not differ significantly between hamartomas associated and not associated with CPP.

CONCLUSION

Anatomic features rather than expression patterns of candidate molecules distinguish hypothalamic hamartomas that are associated with CPP from those that are not.

IN SITU SINGLE-UNIT RECORDING OF HYPOTHALAMIC HAMARTOMAS UNDER ENDOSCOPIC DIRECT VISUALIZATION

OBJECTIVE

Hypothalamic hamartomas (HHs) are associated with refractory epilepsy and are amenable to surgical treatment. The gelastic seizures associated with HHs originate within the HH lesion, but the responsible cellular mechanisms are unknown. Microelectrode patch-clamp recordings from HH neurons in resected slice preparations show that small HH neurons spontaneously fire with intrinsic pacemaker-like activity. We questioned whether spontaneous firing of HH neurons was present in situ, and we hypothesized that single-unit field recordings from HH tissue could be obtained with instrumentation passed through the endoscope before surgical resection.

TECHNIQUE

After informed consent was obtained, patients undergoing transventricular, endoscopic resection of an HH for intractable epilepsy were eligible for study. After placement of the endoscope, a bundled microwire (total of 9 contacts) was placed into the HH under direct visualization. Spontaneous activity was recorded for two or three 5-minute epochs, under steady-state general anesthesia. The wire was advanced 0.5 to 1 mm within the lesion between recording epochs.

RESULTS

A total of thirteen 5-minute recordings were obtained from 5 patients. Noise levels were comparable to extraoperative microwire recordings for temporal lobe epilepsy. Single-neuron spike activity was isolated from a total of 5 channels obtained during recording of 3 sessions in 3 patients.

CONCLUSION

We have shown that single-unit recordings from HH lesions can be successfully obtained in situ under direct endoscopic visualization. We believe that this is the first report using the working channel of a neuroendoscope to make physiological recordings of deep structures in humans.

GABA(A) receptor-mediated excitation in dissociated neurons from human hypothalamic hamartomas

The cellular mechanisms underlying intrinsic epileptogenesis in human hypothalamic hamartoma (HH) are unknown. We previously reported that HH tissue is composed predominantly of GABAergic neurons, but how GABAergic-neuron-rich HH tissue is intrinsically epileptogenic is unclear. Here, we tested the hypotheses that some HH neurons exhibit immature features and that GABA excites these neurons via activation of GABA(A) receptors (GABA(A)Rs). Gramicidin-perforated and cell-attached patch-clamp recordings were performed using freshly-dissociated HH neurons to evaluate GABA(A)R-mediated currents, Cl(-) equilibrium potentials, and intracellular Cl(-) concentrations. Single-cell RT-PCR and immunocytochemical techniques were used to examine cation-Cl(-) co-transporter (NKCC1 and KCC2) gene and KCC2 protein expression and molecular markers of maturation. From a total of 93 acutely-dissociated HH neurons from 34 patients, 76% were small (soma: 6-9 microm) and 24% were large (soma: >20 microm) in size. Under gramicidin-perforated patch recording conditions, GABA(A)R activation depolarized/excited large but hyperpolarized/inhibited small HH neurons in most cases. Compared to small HH neurons, large HH neurons exhibited more positive Cl(-) equilibrium potentials, higher intracellular Cl(-) concentrations, lower KCC2 expression, and an immature phenotype, consistent with GABA(A)R-mediated excitation. Taken collectively, we provide novel evidence for and mechanistic insights into HH epileptogenicity: GABA(A)R-mediated excitation.

GABAA receptor-mediated activation of L-type calcium channels induces neuronal excitation in surgically resected human hypothalamic hamartomas

PURPOSE

The human hypothalamic hamartoma (HH) is a rare, intrinsically epileptogenic lesion associated with gelastic seizures, but the underlying mechanisms remain unclear. Here, we examined the role of GABAA receptors in surgically resected HH tissue.

METHODS

HH tissue slices (350 microm) were studied using cellular electrophysiological, calcium imaging, and immunocytochemical techniques.

RESULTS

Two neuronal cell types were seen: small (10-16 microm) spontaneously firing GABAergic neurons and large (20-28 microm) quiescent neurons. In gramicidin-perforated patch recordings, muscimol (30 microM) induced membrane depolarization in 70% of large (but not small) neurons and a concomitant rise in intracellular calcium. These responses were blocked by bicuculline methiodide (50 microM). Depolarizing neurons also exhibited more positive reversal potentials (Emuscimol) and significantly higher intracellular chloride concentrations compared to those that hyperpolarized. The cation chloride co-transporters NKCC1 and KCC2 were coexpressed in the majority of large neurons, but fluorometric measurements revealed that 84% of large HH neurons expressed solely or relatively more NKCC1. Bumetanide (20 microM), a NKCC1 antagonist, partially suppressed muscimol-induced excitation in large neurons. Concordant with robust expression of CaV1.2 and CaV1.3 subunits in HH neurons, the L-type calcium channel blocker nifedipine (100 microM) prevented muscimol-induced neuronal excitation.

CONCLUSIONS

GABAA receptor-mediated excitation, due in part to differential expression of NKCC1 and KCC2 and subsequent activation of L-type calcium channels, may contribute to seizure genesis in HH tissue. Given the ready availability of L-type calcium channel blockers, our results have clinical ramifications for the treatment of seizures associated with HH lesions.

Identification of somatic chromosomal abnormalities in hypothalamic hamartoma tissue at the GLI3 locus

Hypothalamic hamartomas (HH) are rare, benign congenital tumors associated with intractable epilepsy. Most cases are sporadic and nonsyndromic. Approximately 5% of HH cases are associated with Pallister-Hall syndrome (PHS), which is caused by haploinsufficiency of GLI3. We have investigated the possibility that HH pathogenesis in sporadic cases is due to a somatic (tumor-only) mutation in GLI3. We isolated genomic DNA from peripheral blood and surgically resected HH tissue in 55 patients with sporadic HH and intractable epilepsy. A genome-wide screen for loss of heterozygosity (LOH) and chromosomal abnormalities was performed with parallel analysis of blood and HH tissue with Affymetrix 10K SNP microarrays. Additionally, resequencing and fine mapping with SNP genotyping were completed for the GLI3 gene with comparisons between peripheral blood and HH tissue pairs. By analyzing chromosomal copy-number data for paired samples on the Affymetrix 10K array, we identified a somatic chromosomal abnormality on chromosome 7p in one HH tissue sample. Resequencing of GLI3 did not identify causative germline mutations but did identify LOH within the GLI3 gene in the HH tissue samples of three patients. Further genotyping of 28 SNPs within and surrounding GLI3 identified five additional patients exhibiting LOH. Together, these data provide evidence that the development of chromosomal abnormalities within GLI3 is associated with the pathogenesis of HH lesions in sporadic, nonsyndromic patients with HH and intractable epilepsy. Chromosomal abnormalities including the GLI3 locus were seen in 8 of 55 (15%) of the resected HH tissue samples. These somatic mutations appear to be highly variable.

Clinical application of functional MRI for memory using emotional enhancement: deficit and recovery with limbic encephalitis

Although some functional MRI memory studies show reliable neural activity in the hippocampus and mesial temporal lobe (MTL), most typically report results from group studies. However, fMRI memory probes need to be robust enough to show MTL activity in individual patients to be helpful in diagnosis and treatment planning. We present the case of a patient with non-paraneoplastic limbic encephalitis who had severe anterograde amnesia with subsequent recovery to illustrate a fMRI probe of MTL activity that is easily administered to neurological patients. The task uses emotionally positive and affiliative stimuli to elicit responsivity in the amygdala-hippocampus region. In this patient, weak bilateral hippocampal activation was observed in the acute stage that increased after recovery, paralleling findings on structural MRI and neuropsychological memory assessment. This case study demonstrates that using emotional stimuli to enhance memory responsivity may be an effective way to visualize clinical changes in individual patients.

Anterior motor strip displacement in a boy with right frontal gray matter heterotopia undergoing epilepsy surgery

The case of a 14-year-old boy with behavioral problems and medically refractory epilepsy related to symptomatic gray matter heterotopia in the right frontal lobe is reported. The patient underwent subdural cortical grid placement for seizure localization and functional mapping prior to lesionectomy. On the basis of the patient's MRI scan, it was predicted that the motor cortex was located adjacent to the abnormality, well anterior to its expected location. This prediction was confirmed by stimulation mapping. The patient underwent successful resection of the lesion under the guidance of the cortical map. Postoperatively, his seizures and behavior improved markedly. This case highlights how eloquent cortex can rarely be drawn toward a region of gray matter heterotopia. In addition, he is one of the few reported cases of focal cortical dysplasia resection with resultant improved behavior. These observations of unusual cortical representations have implications in epilepsy surgery planning.

Nonconvulsive status epilepticus in patients suffering spontaneous subarachnoid hemorrhage

OBJECT

Nonconvulsive status epilepticus (NCSE) is an underrecognized and poorly understood complication of aneurysmal subarachnoid hemorrhage (SAH). The authors evaluated the risk factors, electroencephalographic (EEG) characteristics, hospital course, and clinical outcomes associated with NCSE in a population with SAH treated at a single institution.

METHODS

The hospitalization and outcome data were reviewed in 11 patients who had received a diagnosis of NCSE and SAH. The study included individuals from a cohort of 389 consecutive patients with SAH who were treated between March 2003 and June 2005, and who were analyzed retrospectively. The patients' medical history, neurological grade, events of hospitalization, EEG morphological patterns, and disposition were analyzed. Advanced age, female sex, need for ventriculostomy, poor neurological grade (Hunt and Hess Grade III, IV, or V), thick cisternal blood clots, and structural lesions (intracerebral hemorrhage and stroke) were common in the population with NCSE. Patients with normal results on angiograms, good neurological grade (Hunt and Hess Grade I or II), and minimal SAH (Fisher Grade 1 or 2) were at lower risk. The most common ictal patterns were intermittent, and consisted of generalized periodic epileptiform discharges. Medical complications were also frequent, and the outcome of these patients was poor despite aggressive treatment regimens.

CONCLUSIONS

Nonconvulsive status epilepticus is a devastating complication of SAH with a high rate of associated morbidity. Based on these findings it appears that the patients at highest risk for NCSE can be identified, and this should provide a basis for further studies designed to determine the clinical significance of various EEG patterns and to develop preventative strategies.

Hypothalamic hamartoma: basic mechanisms of intrinsic epileptogenesis

The hypothalamic hamartoma (HH) is a rare developmental malformation commonly associated with gelastic seizures that are notoriously refractory to medical therapy. Recent evidence supports the intrinsic seizure propensity of HH. Despite increasing clinical recognition of this condition, the mechanisms of seizure genesis in HH tissue remain unclear. This review summarizes the histochemical and electrophysiological properties of HH neurons, and relates these findings to those characteristics identified in other types of epileptic tissue. Initial studies have revealed two distinct populations of neurons in surgically resected HH tissue. One group consisted of small gamma-aminobutyric acid (GABA)-expressing neurons that occurred principally in clusters and displayed spontaneous rhythmic firing. The second group was composed of large, quiescent, pyramidal-like neurons with more extensive dendritic and axonal arborization. We propose that the small, spontaneously firing GABAergic neurons send inhibitory projections to and drive the synchrony of large output neurons. These observations constitute the basis for future investigations aimed at elucidating the mechanisms of subcortical epileptogenesis.

Chromosomal abnormality at 6p25.1-25.3 identifies a susceptibility locus for hypothalamic hamartoma associated with epilepsy

The pathogenesis of hypothalamic hamartoma (HH) associated with epilepsy is unknown. We have identified an individual with HH and refractory epilepsy exhibiting subtle dysmorphic features. High-resolution karyotype identified a duplication of the terminal end of 6p (6p25.1-25.3), confirmed by fluorescent in situ-hybridization (FISH). Copy number analysis with high-density (250K) single nucleotide polymorphism (SNP) genotyping microarrays characterized the abnormality as a series of amplified regions between 1.4 Mb and 10.2 Mb, with a small tandem deletion from 8.8 Mb to 9.7 Mb. There are 38 RefSeq genes within the duplicated regions, and no known coding sequences within the deletion. This unique patient helps identify 6p25.1-25.3 as a possible susceptibility locus for sporadic HH.

Gelastic seizures misdiagnosed as gastroesophageal reflux disease

Gastroesophageal reflux disease can have variable manifestations including regurgitation, irritability, arching, choking, and apnea. The disorder is also frequently mistaken for seizures (Sandifer syndrome). We report 6 patients in whom the opposite phenomenon occurred: their seizures were mistaken for gastroesophageal reflux disease. Six of 77 patients (6.8%) with gelastic seizures and epilepsy symptomatic of hypothalamic hamartomas were noted to be misdiagnosed with gastroesophageal reflux disease in infancy. As is typical in these patients, gelastic seizures were not diagnosed until months, or often years, later. Delayed diagnosis of hypothalamic hamartomas can lead to a potentially deleterious syndrome involving refractory epilepsy, developmental problems, and precocious puberty. Gelastic seizures should be considered among the conditions that can mimic reflux symptoms.

Electrophysiological properties and subunit composition of GABAA receptors in patients with gelastic seizures and hypothalamic hamartoma

Abnormalities in GABA(A) receptor structure and/or function have been associated with various forms of epilepsy in both humans and animals. Whether this is true for patients with gelastic seizures and hypothalamic hamartoma (HH) is unknown. In this study, we characterized the pharmacological properties and native subunit composition of GABA(A) receptors on acutely dissociated single neurons from surgically resected HH tissues using patch-clamp, immunocytochemical, and RT-PCR techniques. We found that 1) GABA induced an inward current (I(GABA)) at a holding potential of -60 mV; 2) I(GABA) was mimicked by the GABA(A) receptor agonist muscimol and blocked by the GABA(A) receptor antagonist bicuculline, suggesting that I(GABA) was mediated principally through the GABA(A) receptor; 3) the EC(50) and Hill coefficient derived from the I(GABA) concentration-response curve were 6.8 muM and 1.9, respectively; 4) the current-voltage curve was linear at a reversal potential close to zero; and 5) I(GABA) exhibited low sensitivity to zinc and diazepam but higher sensitivity to pentobarbital and pregnanolone. Additionally, using Xenopus oocytes microtransplanted with normal human hypothalamic tissue, we confirmed that the functional properties of GABA(A) receptors were similar to those seen in small isolated HH neurons. Finally, the expression profile of GABA(A) receptor subunits obtained from normal control human hypothalamic tissue was identical to that from surgically resected human HH tissue. Taken together, our data indicate that GABA(A) receptors on small HH neurons exhibit normal pharmacosensitivity and subunit composition. These findings bear relevance to a broader understanding of inhibitory neurotransmission in human HH tissue.

Neurosurgical treatment of status epilepticus

OBJECT

The purpose of this study was to report the cases of five patients with status epilepticus who were treated successfully with neurosurgery.

METHODS

Five children presented with refractory status epilepticus, including complex partial status epilepticus, epilepsia partialis continua and "status gelasticus." Multiple medical therapies had failed to control the seizures, and focal resection was performed. Seizures were fully controlled in four patients, and in one patient seizure frequency was reduced by more than 90%.

CONCLUSIONS

Refractory status epilepticus is associated with a high mortality rate and by definition does not respond well to medical treatment, even optimal medical treatment. Neurosurgical treatment should be considered as another therapeutic option once medical management has failed, and neurosurgery should not necessarily be a last resort.

The Histopathology of Hypothalamic Hamartomas

Hypothalamic hamartomas (HHs) are rare developmental tumors that cause seizures or pituitary axis dysfunction, usually beginning in childhood. We analyzed HH tissue from 57 patients whose tumors were resected through recently developed transcallosal interforniceal and transventricular endoscopic surgical approaches. All cases were composed of abnormally distributed but cytologically normal neurons and glia, including fibrillary astrocytes and oligodendrocytes. Neuronal elements predominated in most cases, but a relative increase in astrocytic elements was seen with increasing age. All had various sized nodular foci of neurons as well as areas of diffusely distributed neurons with interspersed glial cells. Smaller neurons predominated, and most cases had only a few interspersed large ganglion cells. Immunohistochemistry demonstrated extensive production of synapse-associated proteins. Immunohistochemistry for phosphorylated and nonphosphorylated neurofilament and alpha-internexin demonstrated staining patterns consistent with mature neurons. In contrast to cortical dysplasia, atypical large ganglion-like balloon cells were almost never seen. In summary, although their number and distribution vary, mature smaller neurons were the most prominent and most consistent histologic feature of HH. Nodules of these small neurons were a universal feature of the microarchitecture of HH lesions associated with epilepsy. Characterization of these neurons may aid in understanding the mechanism of seizure development in HH.

Hypothalamic Hamartoma and Infantile Spasms

PURPOSE

A small number of patients with hypothalamic hamartoma (HH) present with infantile spasms (IS) as an initial or early seizure type. We describe the clinical features of IS associated with HH.

METHODS

Our series of patients with HH and epilepsy was reviewed to identify cases with a history of IS. The clinical features and neuroradiological findings in this study group were compared to a control group of patients with HH and refractory epilepsy, but without a history of IS.

RESULTS

We identified six patients with HH and a history of IS in this series (n = 122, 4.9%). Five of the six are male. Four of the six patients (67%) developed IS as their first seizure type. The mean age for onset of IS was 6.2 months (range 4-9 months). Results of electroencephalographic (EEG) study at the time of IS diagnosis showed hypsarrhythmia in two (33%). Five patients were treated with adrenocorticotropic hormone (ACTH), and four of the five (80%) responded with control of IS. However, these patients developed other seizure types, and were ultimately refractory to medical management. Aside from the IS, no significant differences in clinical and imaging features were determined between the study group and the control group.

CONCLUSIONS

HH should be included in the differential diagnosis for infants presenting with IS. These patients may have hypsarrhythmia on initial EEG, and may respond to ACTH treatment with improvement of IS. However, all became refractory with other seizure types, more commonly seen in HH patients. Focal pathologies associated with IS may be subcortical, as well as cortical, in nature. We have not identified any predictive features for the occurrence of IS in the HH population.