Suprapineal recess: an alternate site for third ventriculostomy?

✓ This 30-year-old woman presented with clinical symptoms and signs of intracranial hypertension and Parinaud syndrome secondary to ventriculoperitoneal shunt dysfunction. Magnetic resonance (MR) imaging revealed gross triventricular hydrocephalus with a large suprapineal recess due to aqueductal stenosis. Using an endoscopic approach, a ventriculostomy was performed within the floor of the dilated suprapineal recess. Following this procedure the patient experienced alleviation of all her neurological symptoms and signs. Postoperative MR imaging and cerebrospinal fluid flow studies demonstrated a functioning ventriculostomy. The anatomy of the suprapineal recess and its suitability for endoscopic ventriculostomy are discussed.

MR imaging and spectroscopic study of epileptogenic hypothalamic hamartomas: analysis of 72 cases

BACKGROUND AND PURPOSE

Reports of MR imaging in hypothalamic hamartomas associated with epilepsy are few, and the number of patients studied is small. We aimed to detail the relationship of hypothalamic hamartomas to surrounding structures, to determine the frequency and nature of associated abnormalities, and to gain insight into mechanisms of epileptogenesis.

METHODS

We systematically examined MR imaging studies of 72 patients with hypothalamic hamartoma and refractory epilepsy (patient age, 22 months to 31 years). A dedicated imaging protocol was used in 38 cases. Proton MR spectroscopy of the hypothalamic hamartoma was performed for 19 patients and compared with the metabolite profile of the thalamus in 10 normal children and the frontal lobe in 10 normal adults.

RESULTS

Compared with normal gray matter, hypothalamic hamartomas were hyperintense on T2-weighted images (93%), hypointense on T1-weighted images (74%), and had reduced N-acetylaspartate and increased myoinositol content shown by MR spectroscopy. Hypothalamic hamartomas always involved the mammillary region of the hypothalamus, with attachment to one or both mammillary bodies. Intrahypothalamic extension (noted in 97%) tended to displace the postcommissural fornix and hypothalamic gray matter anterolaterally, such that the hypothalamic hamartomas nestled between the fornix, the mammillary body, and the mammillothalamic tract. Larger hamartoma size was associated with central precocious puberty. Associated findings of questionable epileptic significance included anterior temporal white matter signal intensity abnormalities (16%) and arachnoid cysts (6%). Malformations of cortical development were observed in only two patients, and hippocampal sclerosis was not observed.

CONCLUSIONS

Hypothalamic hamartomas can be readily distinguished from normal hypothalamic gray and adjacent myelinated fiber tracts, best appreciated on thin T2-weighted images. MR imaging and spectroscopy suggest reduced neuronal density and relative gliosis compared with normal gray matter. Associated epileptogenic lesions are rare, supporting the view that the hypothalamic hamartoma alone is responsible for the typical clinical features of the syndrome. The intimate relationship to the mammillary body, fornix, and mammillothalamic tract suggests a role for these structures in epileptogenesis associated with hypothalamic hamartomas.

Hypothalamic hamartoma with refractory epilepsy: surgical procedures and results in 18 patients

AIM

To study the surgical procedures and results on seizures, in 18 patients with refractory epilepsy due to hypothalamic hamartoma.

PATIENTS AND METHODS

Eighteen patients aged from 9 months to 32 years underwent surgery between 1997 and 2002. The mean age at seizure onset was 15.5 months. Seventeen patients had gelastic seizures, 14 had partial seizures, two had infantile spasms, 10 had tonic or atonic seizures and three had generalized seizures. The mean seizure frequency was 21 per day. Four patients had borderline intellectual disability and the others were mentally retarded. Five patients had precocious puberty, one had acromegaly and four suffered from obesity. Brain MRI, performed at least twice in each patient showed the hamartoma as a stable, homogeneous interpeduncular mass implanted either on the mammillary tubercle or on the wall of the third ventricle, with variable extension to the bottom. Ictal SPECT, performed in four patients, showed hyperperfusion within the hamartoma in two.

SURGICAL PROCEDURE

Twenty-six operations were performed in 18 patients. The first patient underwent a total removal of the hamartoma, whereas the following patients underwent a disconnection, either through open surgery (14 patients) or endoscopy (10 patients).

RESULTS

Regarding the seizure outcome with a mean follow up of three years four months (one year to 4.5 years), nine patients are seizure-free, one patient has only brief gelastic seizures and eight are dramatically improved. Surgery was uncomplicated in all but two patients: one had transitory hemiplegia and paresis of the third cranial nerve, the other presented with hemiplegia due to ischemia of the middle cerebral artery territory. The quality of life, behavior and school performance were greatly improved in most of the patients.

CONCLUSION

Our series illustrates the feasibility and relative safety of disconnecting surgery of hypothalamic hamartomas, with seizure relief in 50% and a dramatic improvement in the others. Endoscopic disconnection seems to be a very safe way to treat the intra-ventricular part of hamartomas.

Are some memory deficits unique to lesions of the mammillary bodies?

The role of the mammillary bodies in human memory is still in debate. A recent model of human amnesia proposes similar functions for the mammillary bodies and the hippocampus. But the main evidence for this model comes from animal studies using the delayed non-matching to sample paradigm. We describe a patient who developed a severe memory impairment after surgical removal of a germinoma. Postsurgical high resolution MRI revealed bilaterally shrunken mammillary bodies and an infarct of the left mammillary body. There were no other relevant lesions. Neuropsychological testing showed mildly impaired frontal lobe functions (executive functions, working memory and word fluency), almost intact learning and recognition, but severely impaired free and delayed recall. Experimental investigations revealed a reduced but preserved release of proactive interference and a pronounced impairment of recency and source judgments. We conclude that the mammillary bodies do play a prominent role in human memory, although the role differs slightly from that of the hippocampus.

Stereotactic radiofrequency ablation for the treatment of gelastic seizures associated with hypothalamic hamartoma. Case report

The author presents the case of a patient with gelastic seizures associated with a hypothalamic hamartoma, in whom partial resection of the hamartoma followed by temporal lobectomy and orbitofrontal corticectomy failed to reduce the seizures. Subsequent stereotactic radiofrequency ablation of the hamartoma resulted in progressive improvement in the seizure disorder during a 28-month follow-up period. There is support in the literature for the concept that gelastic seizures originate directly from the hamartoma; however, direct surgical approaches to these lesions pose significant risks. It is proposed that the technique of radiofrequency ablation provides a minimally invasive, low-risk approach for the treatment of hypothalamic hamartomas.

Preoptic area grafts implanted in mammillary bodies of hypogonadal mice: patterns of GnRH neuronal projections

Gonadotropin-releasing hormone (GnRH) axons project to the median eminence, where the peptide is released to stimulate pituitary gonadotrophs. Hypogonadal mice (hpg) do not synthesize GnRH due to a deletion in the gene. When neonatal preoptic area (POA) tissue from normal mice containing GnRH neurons is transplanted into the third ventricle of hpg mice, GnRH axons exit the graft and specifically project to the median eminence, where the release of GnRH in the portal circulation induces the stimulation of the pituitary-gonadal axis. To test the hypothesis that the median eminence region is critical to targeting, we placed POA grafts in the region of the mammillary bodies, which never contains GnRH cell bodies, but is nevertheless close to the median eminence. Control mice received bilateral grafts into the anterior hypothalamus. GnRH axons innervated the median eminence in animals with grafts in the mammillary bodies and posterior hypothalamus. Mice with such grafts for 4-5 months had gonadal development, while those with grafts for shorter periods did not. Anterior hypothalamic grafts merged into the third ventricle and, consistent with previous studies, this resulted in GnRH innervation of the median eminence and gonadal development. However, when grafts were located within dorsal regions such as the thalamus, no median eminence innervation was seen. In these cases, GnRH axons borrowed other bundles of fibers to travel within the host brain. The pattern of innervation from grafts within ventro-caudal regions of the hypothalamus vs. that from dorsal regions supported the hypothesis that the median eminence releases diffusible substances directing GnRH outgrowth.

MRI of the fornix and mamillary body in temporal lobe epilepsy

We performed MRI on 27 patients with clinically proven temporal lobe epilepsy (TLE), all with prior EEG lateralisation, and 10 volunteers, studied to evaluate disparity in size arising from biological variation (group 1). Three-dimensional spoiled GRASS (3DSPGR) sequences provided 2-mm contiguous sections of the limbic system, enabling assessment of the hippocampus (HC), fornix (FN) and mamillary body (MB). Measurements of FN and MB width were made from a workstation. Any percentage difference in size was computed. In 19 cases there was unilateral abnormality in the HC (group 2); in 18 and 19 cases respectively there was a smaller FN and MB on the same side as the abnormal HC. This percentage difference in size was significantly greater than that in group 1 in the FN and MB in 17 and 17 cases respectively. Comparison of percentage difference computations for FN and MB between groups 1 and 2 showed high statistical significance (P < 0.0002). In 5 patients with clinical TLE the HC was normal on MRI (group 3). Unequal FN and MB sizes were found in 4, significant in 2. Comparison of percentage difference computations for FN and MB showed statistical significance (P < 0.0005 and P < 0.0003 respectively). There was no case of discordance between the sides of hippocampal abnormality and the smaller FN or MB or between the sides of smaller FN and MB. The strong concordance between the changes in the HC and those in the FN and MB suggests that this combination will play an important role in the assessment of TLE and limbic system abnormality.

Hypothalamic hamartomas: with special reference to gelastic epilepsy and surgery

This study presents six patients with hypothalamic hamartomas diagnosed on the basis of magnetic resonance imaging. Histological confirmation was performed in three patients who underwent surgery. Immunohistological assays were used to determine the neurosecretory pattern. Four patients presented with epilepsy, including gelastic seizures. Other symptoms included behavioral abnormalities in four patients and precocious puberty and visual impairment in two patients. One patient presented associated developmental defects. Good results without morbidity were achieved with surgical resectioning in two patients with large hamartomas associated with behavioral abnormalities and gelastic epilepsy that was unresponsive to conventional medical treatment and in one patient with visual impairment. We propose a classification of the hypothalamic hamartomas based on topographical and clinical data obtained from 36 selected cases in the literature and six of our own cases. This classification should help to classify the various treatment methods and the surgical risks into four subgroups (Types la, lb, lla, and llb). We conclude that the surgical approach is a realistic alternative in certain cases, including large and broad-based Type llb hamartomas associated with gelastic epilepsy and behavioral disorders.

Adrenal response to acute stress in mammillary medial nuclei lesioned rats

In view of the inhibitory influence of Mammillary Medial Nuclei, pars lateralis (MMN) on corticoadrenal activity, experiments were conducted in order to determine whether these nuclei are involved in the control of adrenal response to ether stress. In bilateral MMN lesioned rats, prestress plasma corticosterone concentration (C) is significantly higher than that in sham lesioned animals. Acute stress produced a significant C increase in both, sham and lesioned rats, being this increase lower in lesioned animals. After exposure to ether vapors. adrenal concentration of norepinephrine was similar in lesioned and control animals. Whereas, adrenal epinephrine concentration was significantly higher in lesioned rats than that found in the sham lesioned ones. This study demonstrates that the integrity of MMN is not essential for adrenal response to acute stress.

Ablations of the mammillary nuclei in monkeys: effects on postoperative memory

A new procedure was developed for ablating the mammillary nuclei in nonhuman primates via direct visual exposure. Using this technique, monkeys receiving lesions of the mammillary nuclei were compared to control animals after surgery to assess the retention of preoperatively acquired visuospatial discriminations and subsequent postoperative ability to attain a demanding spatial memory task. Although the lesions proved to be accurate and complete, no changes in gross behavior or deficits in preoperatively acquired visual and spatial behaviors were noted. The monkeys with mammillary body lesions were, however, impaired in their ability to acquire postoperatively the demanding spatial memory task. These findings are consistent with previous investigations suggesting that the mammillary bodies are involved in the acquisition of spatial discriminations and skills.