Mediobasal Temporal Lobe Research Articles

Influence of radiotherapy on control functions network fMRI connectivity in patients with lateralized mediobasal temporal lesions

According to the literature, radiotherapy (RT) used for brain tumors, along with a positive effect, can be accompanied by negative consequences in the form of the development of neurocognitive deficit due to the side effects of radiation on critical brain structures. At the same time, there are indications of a possible modulation of hippocampal neurogenesis with subsequent activation of a number of cognitive functions. An important component of human cognitive activity is the so-called executive functions (EF), which include the initiation, planning, regulation and control of any purposeful activity. Their structural and functional support is currently associated with the prefrontal and parietal sections of the hemispheres, as well as with the formations of the lower temporal cortex and the hippocampus. The work is aimed at dynamic assessment of the state of the EF-network according to the analysis of resting fMRI connectivity before and after 6 months after RT. In dynamics, 14 patients with lateralized tumor lesions of the mediobasal temporal lobe were examined: 7 with the left side, 7 with the right side. The control group consisted of 9 healthy subjects. Each participant underwent fMRI at rest – with further analysis of the functional connectivity between the given regions of interest, corresponding to the topography of the EF-network. The results were compared with the MRI morphometry tumor data. It has been shown that in patients 6 months after RT, against the background of a decrease in volume or stabilization of tumor growth, the functional effects are ambiguous and depend on the lateralization of the lesion: with a right-sided lesion they tend to normalize, while with a left-sided lesion they increase.

The infratranstentorial subtemporal approach (ITSTA): a valuable skull base approach to deep-seated non-skull base pathology.

Surgical access to space-occupying lesions such as tumors and vascular malformations located in the area of the tentorial notch, mediobasal temporal lobe, and para-midbrain is difficult. Lesions in this area are typically resected with supratentorial approaches demanding significant elevation of the temporal lobe or even partial lobectomy, or via a supracerebellar transtentorial approach. We introduce an alternative, the skull base infratranstentorial subtemporal approach (ITSTA), which provides excellent exposure of the incisural area while minimizing risk to the temporal lobe. We included consecutive patients with pathology involving the area of the tentorial incisura, para-midbrain, and mediobasal temporal area who underwent surgery via ITSTA from 2012 to 2018. The approach includes partial mastoidectomy, temporal craniotomy, and tentorial section. Space obtained by mastoidectomy provides a sharp high-rising angle-of-attack, significantly diminishing the need for temporal lobe retraction. Surgeries were performed using microsurgical techniques, neuronavigation, and electrophysiological monitoring. Clinical presentation, tumor characteristics, extent of resection, complications, and outcome were retrospectively reviewed under a waiver of informed consent. Nine patients met inclusion criteria (five female, four male; mean age 44years, range 7-72). They underwent surgery for removal of para-midbrain arteriovenous malformation (AVM, 3/9), medial tentorial meningioma (2/9), mediobasal epidermoid cyst (2/9), oculomotor schwannoma (1/9), or pleomorphic xanthoastrocytoma (PXA) of the fusiform gyrus (1/9). Three AVMs were removed completely; among six patients with tumors, gross total resection was achieved in three and subtotal resection in three. All surgeries were uneventful without complications. There were no new permanent neurological deficits. At late follow-up (mean 42.5months), eight patients had a Glasgow Outcome Score (GOS) of 5. One 66-year-old female died 18months after surgery for reasons not related to her disease or surgery. The ITSTA is a valuable skull base approach for removal of non-skull base pathologies located in the difficult tentorial-incisural parabrainstem area.

Precortical Phase of Alzheimer's Disease (AD)-Related Tau Cytoskeletal Pathology.

Alzheimer's disease (AD) represents the most frequent progressive neuropsychiatric disorder worldwide leading to dementia. We systematically investigated the presence and extent of the AD-related cytoskeletal pathology in serial thick tissue sections through all subcortical brain nuclei that send efferent projections to the transentorhinal and entorhinal regions in three individuals with Braak and Braak AD stage 0 cortical cytoskeletal pathology and fourteen individuals with Braak and Braak AD stage I cortical cytoskeletal pathology by means of immunostainings with the anti-tau antibody AT8. These investigations revealed consistent AT8 immunoreactive tau cytoskeletal pathology in a subset of these subcortical nuclei in the Braak and Braak AD stage 0 individuals and in all of these subcortical nuclei in the Braak and Braak AD stage I individuals. The widespread affection of the subcortical nuclei in Braak and Braak AD stage I shows that the extent of the early subcortical tau cytoskeletal pathology has been considerably underestimated previously. In addition, our novel findings support the concept that subcortical nuclei become already affected during an early 'pre-cortical' evolutional phase before the first AD-related cytoskeletal changes occur in the mediobasal temporal lobe (i.e. allocortical transentorhinal and entorhinal regions). The very early involved subcortical brain regions may represent the origin of the AD-related tau cytoskeletal pathology, from where the neuronal cytoskeletal pathology takes an ascending course toward the secondarily affected allocortex and spreads transneuronally along anatomical pathways in predictable sequences.

Cognitive Profiles of Patients with Mild Cognitive Impairment or Dementia in Alzheimer's or Parkinson's Disease

Background: Alzheimer's disease (AD) and Parkinson's disease (PD) are associated with severe cognitive decline, but it is still unclear to what extent they become functionally more similar over time. Methods: We compared amnestic mild cognitively impaired (aMCI; n = 29) patients to mild cognitively impaired (MCI) PD patients (n = 25), and patients with AD (n = 34) to patients with PD dementia (PDD; n = 15) with respect to cognitive functioning and mood. Results: aMCI patients were impaired in episodic memory, while MCI PD patients showed deficits in visuoconstruction and attention. AD and PDD patients showed comparable deficits on tests for language, attention and visuoconstruction. However, unlike PDD patients but similar to aMCI patients, AD patients showed a characteristic memory impairment, especially commission errors on recognition tasks, whereas PDD patients scored higher on the depressive mood questionnaire. Conclusions: In advanced stages of both diseases, the pattern of functional deficits associated with parietal and temporal lobe functions (attention, visuoconstruction and language) is similar. However, specific differences, already present in the early stage (recognition errors in AD, associated with mediobasal temporal lobe functioning, and depressed mood in PDD, associated with non-motor basal ganglia loops), are also observed in the late stage.

Microsurgical anatomy of the transsylvian translimen insula approach to the mediobasal temporal lobe: Technical considerations and case illustration

Background:Various vascular, neoplastic, and epileptogenic pathologies occur in the mediobasal temporal region. A transsylvian translimen insula (TTI) approach can be used as an alternative to temporal transcortical approach to the mediobasal temporal region. The aim of this study was to demonstrate the surgical anatomy of the TTI approach, including the gyral, sulcal, and vascular anatomy in and around the limen insula. The use of this approach is illustrated in the resection of a complex arteriovenous malformation.Methods:The TTI approach to the mediobasal temporal region was performed on three silicone-injected cadaveric heads. The gyral, sulcal, and arterial anatomy of the limen insula was studied in six formalin-fixed injected hemispheres.Results:The TTI approach provided access to the anterior and middle segments of the mediobasal temporal lobe region as well as allowing access to temporal horn of the lateral ventricle. Using this approach we were able to successfully resect an arteriovenous malformation of the dominant medial temporal lobe.Conclusion:The TTI approach provides a viable surgical route to the region of mediobasal temporal lobe region. This approach offers an advantage over the temporal transcortical route in that there is less risk of damage to optic radiations and speech area in the dominant hemisphere.

Supracerebellar transtentorial approach—resection of the tentorium instead of an opening—to provide broad exposure of the mediobasal temporal lobe: anatomical aspects and surgical applications

The aim of this study was to describe the surgical anatomy of the mediobasal aspect of the temporal lobe and the supracerebellar transtentorial (SCTT) approach performed not with an opening, but with the resection of the tentorium, as an alternative route for the neurosurgical management of vascular and tumoral lesions arising from this region. Cadaveric specimens were used to illustrate the surgical anatomy of the mediobasal region of the temporal lobe. Demographic aspects, characteristics of lesions, clinical presentation, surgical results, follow-up findings, and outcomes were retrospectively reviewed for patients referred to receive the SCTT approach with tentorial resection. Ten patients (83%) were female and 2 (17%) were male. Their ages ranged from 6 to 59 years (mean 34.5 ± 15.8 years). All lesions (3 posterior cerebral artery aneurysms, 3 arteriovenous malformations, 3 cavernous malformations, and 3 tumors) were completely excluded or resected. After a mean follow-up period of 143 months (range 10-240 months), the mean postoperative Glasgow Outcome Scale score was 4.9. Knowledge of the surgical anatomy provides improvement for microsurgical approaches. The evolution from a small opening to a resection of the tentorium absolutely changed the exposure of the mediobasal aspect of the temporal lobe. The SCTT approach with tentorial resection is an excellent alternative route to the posterior part of mediobasal aspect of the temporal lobe, and it was enough to achieve the best neurosurgical management of tumoral and vascular lesions located in this area.

Personality correlates of sphenoidal EEG-foci in temporal lobe epilepsy.

Patients with unilateral temporal lateral or temporal mediobasal epileptic focus as ascertained by sphenoidal electrode EEG recordings were evaluated using the questionnaire designed by Bear & Fedio (1977). The seventeen traits defined by the items in this questionnaire were also assessed by close observers in an equivalent questionnaire. Patients with medio-basal temporal lobe focus were found generally to exhibit "epileptic" personality traits to a greater extent than patients with lateral focus, and the results indicated that they also, more than patients with lateral focus, were characterized by a schizoid paranoid outlook. The patients with left temporal lobe focus were found to be emotionally labile compared to patients with right temporal lobe focus. Patients with lateral right-sided temporal focus had obviously the most benign psychological prognosis. The main discrepancies between the results of Bear & Fedio (1977) and the present study are briefly discussed.

MICROSURGICAL ANATOMY OF THE SUPRACEREBELLAR TRANSTENTORIAL APPROACH TO THE POSTERIOR MEDIOBASAL TEMPORAL REGION

Surgical access to the posterior portion of the mediobasal temporal lobe presents a formidable challenge to neurosurgeons, and much controversy still exists regarding the selection of the surgical approach to this region. The supracerebellar transtentorial (SCTT) approach to the posterior mediobasal temporal region can be used as an alternative to the subtemporal or transtemporal approaches. The aim of this study was to demonstrate the surgical anatomy of the SCTT approach and review the gyral, sulcal, and vascular anatomy of the posterior mediobasal temporal lobe. The use of this approach in the resection of a ganglioglioma located in the left posterior parahippocampal gyrus is illustrated. The SCTT approach to the posterior parahippocampal gyrus was performed on three silicone-injected cadaveric heads. The gyral, sulcal, and arterial anatomy of the posterior mediobasal temporal lobe was studied in six formalin-fixed injected hemispheres. The SCTT approach provided a direct path to the posterior mediobasal temporal lobe and exposed the posterior parahippocampal gyrus as well as the adjacent gyri in all of the cadaveric specimens. Through this approach, gross total resection of the ganglioglioma was possible in our patient. The SCTT approach provided a viable surgical route to the posterior mediobasal temporal lobe in the cadaveric studies. This approach provides an advantage over the subtemporal and transtemporal routes in that there is less temporal lobe retraction.

Radiosurgery of functioning pituitary adenomas: Comparison of different treatment techniques including dynamic and conformal arcs, shaped beams, and IMRT

Purpose: Evaluation of different techniques including intensity-modulated radiotherapy (IMRT) for stereotactic radiosurgery (SRS) of pituitary adenoma (PA). Methods and Materials: Between January 2003 and February 2005, 152 SRS procedures were performed. Ten patients with PA were compared: conformal vs. dynamic arc treatment with micromultileaf collimator (mMLC) vs. circular collimators vs. 8–10 conformal static mMLC beams with and without IMRT. Prescribed total dose: 18 Gy (90%). Constraints: D max optic chiasm 10Gy temporal lobe 10Gy temporal lobe. Results: For the end point "improvement in coverage," an advantage with IMRT was noted for 5 of 10 patients as compared with the dynamic arc approach. Volume treated >18 Gy outside the planning target volume was lowest in 9 of 10 patients after IMRT; 1 patient achieved better conformity with circular collimators. As for Vol 10Gy temporal lobe, an advantage was depicted for 1 of 10 patients with IMRT, the other techniques appearing equally effective in shielding the temporal lobe. With all techniques Vol 10 Gy temporal lobe was max optic chiasm Conclusions: Novalis-based radiosurgery using dynamic arc treatment with mMLC is considered a safe and appropriate approach for SRS of PA.

Meyer's Loop and the Optic Radiations in the Transsylvian Approach to the Mediobasal Temporal Lobe

In the transsylvian approach to the mediobasal temporal structures, the temporal horn is approached through the floor of the sylvian fissure. The anterior bundle of the optic radiations (Meyer's loop) courses between the floor of the sylvian fissure and roof of the temporal horn and could be damaged in this approach. This study was designed to define the route through the floor of the sylvian fissure least likely to damage the optic pathways. Meyer's loop was dissected by applying Klingler's fiber dissection technique in 10 formalin-fixed human hemispheres. Several measurements quantified the relationship of the Meyer's loop to surgically important structures. This study identified a triangular safe area below the floor of the sylvian fissure through which the temporal horn could be accessed in the transsylvian approach with a low risk of damaging the optic radiations. An incision in the floor of the sylvian fissure directed downward at the level of limen insula and the adjacent 5 mm of the inferior insular sulcus would avoid the optic radiations. An incision directed straight downward 10, 15, and 20 mm behind the limen in the inferior insular sulcus would cross Meyer's loop and would need to be directed downward and medially as much as 80 degrees from the sagittal plane to avoid Meyer's loop. In the transsylvian approach to the temporal horn, incisions at the level of the limen, or adjacent 5 mm of the inferior insular sulcus, are less likely to damage Meyer's loop and the optic radiations than more posterior incisions along the inferior insular sulcus. Incision at this safe level commonly opens into the amygdala, a portion of which is removed to provide entry into the temporal horn for removal of the mediobasal structures.

Aortic dissection presenting with transient global amnesia-like symptoms

Diagnostic criteria of transient global amnesia (TGA) are witnessed attacks, clear-cut anterograde amnesia during the attack, absent clouding of consciousness and loss of personal identity, no accompanying focal neurologic symptoms or epileptic features, resolution of attacks within 24 hours, and no recent head injury or active epilepsy.1 For the etiology of TGA, four main hypotheses have been considered: TIA, epilepsy, migraine, and transient venous ischemia.1–3⇓⇓ None of these hypotheses fully explains the mechanism of this episodic disease, but the accepted neuroanatomic correlate of TGA is the mediobasal temporal lobe and hippocampus. We present two patients with aortic dissection who provide evidence for an ischemic pathogenesis in TGA. ### Patient 1. A 47-year-old man was found confused and disoriented. On examination at admission, he asked repetitive questions and was alert but completely disoriented to time and place and only partially oriented to person. The cranial nerve examination showed only a slight anisocoria. The …

Combined MEG/EEG analysis of the interictal spike complex in mesial temporal lobe epilepsy

We studied the functional organization of the interictal spike complex in 30 patients with mesial temporal lobe epilepsy (MTLE) using combined magnetoencephalography (MEG)/electroencephalography (EEG) recordings. Spikes could be recorded in 14 patients (47%) during the 2- to 3-h MEG/EEG recording session. The MEG and EEG spikes were subjected to separate dipole analyses; the MEG spike dipole localizations were superimposed on MRI scans. All spike dipoles could be localized to the temporal lobe with a clear preponderance in the medial region. Based on dipole orientations in MEG, patients could be classified into two groups: patients with anterior medial vertical (AMV) dipoles, suggesting epileptic activity in the mediobasal temporal lobe and patients with anterior medial horizontal (AMH) dipoles, indicating involvement of the temporal pole and the anterior parts of the lateral temporal lobe. Whereas patients with AMV dipoles had strictly unitemporal interictal and ictal EEG changes during prolonged video-EEG monitoring, 50% of patients with AMH dipoles showed evidence of bitemporal affection on interictal and ictal EEG. Nine patients underwent epilepsy surgery so far. Whereas all five patients with AMV dipoles became completely seizure-free postoperatively (Class Ia), two out of four patients with AMH dipoles experienced persistent auras (Class Ib). This difference, however, was not statistically significant. We therefore conclude that combined MEG/EEG dipole modeling can identify subcompartments of the temporal lobe involved in epileptic activity and may be helpful to differentiate between subtypes of mesial temporal lobe epilepsy noninvasively.

High prevalence of thorn-shaped astrocytes in the aged human medial temporal lobe

Thorn-shaped astrocytes (TSA) are glial fibrillary tangles that contain abnormally phosphorylated and aggregated microtubule-associated tau protein. The present study examines the prevalence of TSA in the human medial temporal lobe of 100 autopsy brains aged 42–97 years (mean age: 65 years). Serial brain sections were cut at 100 μm and stained using phosphorylation-dependent anti-tau antibodies (AT8, PHF-1, TG3, Alz-50) and silver staining methods for neurofibrillary changes and β-amyloid deposits. TSA preferentially were distributed in periventricular, subependymal, and subpial areas of the mediobasal temporal lobe (MTL). Double-labeling with AT8 and anti-GFAP antibodies demonstrated that the abnormal tau protein was deposited in astroglial cell bodies and in proximal and distal astroglial processes. A pronounced inter-individual variation was noted in the density of AT8-positive TSA, thereby allowing distinction of mild, moderate, and severe involvement. TSA were absent in individuals younger than 60 years. A significant increase in the prevalence of TSA was noted with advancing age. In the age-range of 75–98 years TSA were found in approximately 50% of all individuals. The development of TSA was not correlated with the severity of Alzheimer-related cortical pathology. In summary, this study suggests that TSA is a distinct form of glial tau pathology that occurs with a high frequency in elderly individuals.

Limbic epileptogenesis: a model study using kindling from the amygloid cortical nucleus.

The dynamics of limbic epileptogenesis was studied using a model of electrical kindling from different rostrocaudal segments of the cortical nucleus of the amygdala (CoA). Statistically significant relationships were found between the rostrocaudal location of the site of focal stimulation of the CoA and the behavioral and electrographic manifestations of seizure activity. The data obtained suggest that different rostrocaudal segments of the CoA play different roles in the genesis of limbic epilepsy. Temporal lobe epilepsy (or limbic epilepsy) is the most common form of this disease in humans [3, 10, 11]. Patients with this form of epilepsy suffer from complex partial (focal) and secondarily generalized seizures. In most cases, pharmacological resistance develops that makes it difficult to efficiently control seizures or significantly decrease their frequency using anticonvulsant drugs [13]. Because of the high incidence of temporal lobe epilepsy, difficulties in its pharmacotherapy, and the diversity of associated structural and functional brain lesions, of particular interest are experimental studies in which the pathogenetic mechanisms of temporal epilepsy are analyzed using various animal models [9, 10]. Electrical kindling (low-level stimulation that causes a progressively increasing response when applied repeatedly) [8] is the most adequate chronic model of temporal epilepsy that closely follows the natural course of its development with respect to a number of parameters [3‐6, 9, 10]. The role of the CoA in initiating the epileptiform activity of the amygdaloid complex (AC) and of the entire brain remains largely obscure. Our early studies [4, 5] and a recent study by Pitkanen et al. [11] implicated the CoA in spreading the seizure activity, especially in generating mirror foci in the amygdala of the contralateral hemisphere. In contrast, Cain [7] presents evidence that the CoA is of little significance in the epileptogenic process. However, taken together, the fact that the CoA is morphologically closely related to the piriform cortex and to some other structures of the AC in the ipsi- and contralateral hemispheres, and the clinical data indicating that the mediobasal temporal lobe is involved in the genesis of human temporal lobe epilepsy put in doubt Cain’s point of view. In the rat AC, the CoA lies medial to the piriform cortex, being partially exposed on the basal surface of the brain [1, 2]. The CoA is elongated rostrocaudally. This makes it possible to perform separately microstimulation of its anterior and posterior subniclei, which are known for their complex and heterogeneous structure [2]. The CoA can be divided into the anterior CoA (CoAa), the periamygdaloid cortex (PAC), and the posterior CoA (CoAp), based on the differences in their neuron composition, cytoarchitectonics, histochemistry, afferentation, and involvement in the main conducting systems of the AC [1]. The purpose of this study was to determine whether the behavioral and electrographic manifestations of epileptogenesis depend on the rostrocaudal location of the site of focal stimulation.

Neuromagnetic recordings in temporal lobe epilepsy.

The introduction of whole-head magnetoencephalography (MEG) systems facilitating simultaneous recording from the entire brain surface has established MEG as a clinically feasible method for the evaluation of patients with temporal lobe epilepsy (TLE). In mesial TLE, two types of MEG spike dipoles could be identified: an anterior vertical and an anterior horizontal dipole. Dipole orientations can be used to attribute spike activity to temporal lobe subcompartments. Whereas the anterior vertical dipole is compatible with epileptic activity in the mediobasal temporal lobe, the anterior horizontal dipole can be explained by epileptic activity of the temporal tip cortex. In nonlesional TLE, medial and lateral vertical dipoles were found which could distinguish between medial and lateral temporal seizure onset zones as evidenced from invasive recordings. In lesional TLE, MEG could clarify the spatial relationship of the structural lesion to the irritative zone. Evaluation of patients with persistent seizures after epilepsy surgery may represent another clinical important application of MEG because magnetic fields are less influenced than electric fields by the prior operation. Simultaneous MEG and invasive EEG recordings indicate that epileptic activity restricted to mesial temporal structures cannot reliably be detected on MEG and that an extended cortical area of at least 6 to 8 cm2 involving also the basal temporal lobe is necessary to produce a reproducible MEG signal. In lateral neocortical TLE MEG seems to be more sensitive than scalp-EEG which further underlines the potential role of MEG for the study of nonlesional TLE. Whole-head MEG therefore can be regarded as a valuable and clinically relevant noninvasive method for the evaluation of patients with TLE.

Dipole source localization of interictal epileptiform activity in temporal lobe epilepsy with medial temporal lesion

Dipole sources of interictal epileptiform activities recorded by conventional electroencephalogram (EEG) were estimated using the dipole tracing method. Four cases of temporal lobe epilepsy with medial temporal lesions were studied. Two patients with hippocampal sclerosis, one patient with granulation in the hippocampus and one patient with cavernous angioma were involved in the study. Interictal epileptiform activities were classified into two patterns according to the topography of spikes. They were widespread spikes over the parasagittal electrodes (parasagittal spikes) and restricted spikes at the temporal electrodes (temporal spikes). Dipole sources of parasagittal spikes were localized in the medio-basal temporal lobe with vertically orientated vector moment. Dipole sources of temporal spikes were localized in the medio-basal temporal lobe with horizontally orientated vector moment. Locations of dipoles and directions of vector moments were consistent with topography and polarity of spikes. The difference in the two patterns of interictal epileptiform activities was derived from the difference in the direction of the vector moment of dipole sources. There was no difference in the location of dipole sources. Both the dipole sources and the lesions were localized in the same medio-basal temporal lobe. Dipole tracing was very useful in localizing the dipole sources of interictal epileptiform activities and in understanding the neurophysiological background.

Schizophrenia-like psychosis and epilepsy: the status of the association.

Current knowledge of the relationship between epilepsy and schizophrenia-like psychosis is examined, and the proposed pathogenetic mechanisms are evaluated. The author provides an overview of the published literature on epilepsy and schizophrenia-like psychosis. The schizophrenia-like psychoses of epilepsy are inadequately categorized by the current classifications. Their categorization into ictal, postictal, and interictal psychoses is clinically useful, but it does not imply distinct pathophysiology for each. The recent interest in postictal psychoses has opened an important avenue for research. Brief interictal psychoses, involving alternation between epilepsy and psychosis and accompanied by forced normalization, are uncommon. Many aspects of the relationship with chronic interictal psychosis remain controversial. The majority of investigators support a special but not exclusive relationship with mediobasal temporal lobe epilepsy, and left temporal bias receives only limited support. The chronic psychosis resembles schizophrenia phenomenologically. Some suggested risk factors are severe and intractable epilepsy, epilepsy of early onset, secondary generalization of seizures, certain anticonvulsant drugs, and temporal lobectomy. Different neuropathological studies suggest the presence of cortical dysgenesis or diffuse brain damage. There are many mechanisms by which epilepsy may be associated with schizophrenia-like psychosis. It is likely that structural brain abnormalities, e.g., cortical dysgenesis or diffuse brain lesions, underlie both epilepsy and psychosis, and that the seizures modify the presentation of the psychosis, and vice versa, thus producing a clinical picture of both an affinity and an antagonism between the two disorders.

S.11.05 - Role of inflammation, Apo E, and antichymotrypsin in Alzheimer's disease

Thorn-shaped astrocytes (TSA) are glial fibrillary tangles that contain abnormally phosphorylated and aggregated microtubule-associated tau protein. The present study examines the prevalence of TSA in the human medial temporal lobe of 100 autopsy brains aged 42–97 years (mean age: 65 years). Serial brain sections were cut at 100 μm and stained using phosphorylation-dependent anti-tau antibodies (AT8, PHF-1, TG3, Alz-50) and silver staining methods for neurofibrillary changes and β-amyloid deposits. TSA preferentially were distributed in periventricular, subependymal, and subpial areas of the mediobasal temporal lobe (MTL). Double-labeling with AT8 and anti-GFAP antibodies demonstrated that the abnormal tau protein was deposited in astroglial cell bodies and in proximal and distal astroglial processes. A pronounced inter-individual variation was noted in the density of AT8-positive TSA, thereby allowing distinction of mild, moderate, and severe involvement. TSA were absent in individuals younger than 60 years. A significant increase in the prevalence of TSA was noted with advancing age. In the age-range of 75–98 years TSA were found in approximately 50% of all individuals. The development of TSA was not correlated with the severity of Alzheimer-related cortical pathology. In summary, this study suggests that TSA is a distinct form of glial tau pathology that occurs with a high frequency in elderly individuals.

Involvement of a direct neural mechanism in the control of gonadal functions.

Much time has been devoted to study of the hypothalamo-hypophyseal-gonadal axis. However, there is now evidence of a complementary control mechanism for the gonads, namely a pituitary-independent, direct neural link that exists between the central nervous system and the gonads. We investigated whether mediobasal temporal lobe structures could control gonadal functions by a purely neural mechanism or whether they acted through the classical hypothalamo-hypophyseal system. Right- or left-sided deafferentiation of the temporal lobe was combined with right- or left-sided hemicastration in adult and prepubertal male and female rats. In adult females right-sided deafferentiation, regardless of the side of hemiovariectomy significantly reduced the extent of compensatory ovarian hypertrophy. Similar lesions on the left side did not interfere with the usual compensatory ovarian growth. This difference in compensatory hypertrophy between right- and left-sided lesioned rats was observed even in the face of a significant drop in serum LH concentrations in both groups. In pre- and postpubertal females temporal lobe lesion in either side was unable to alter compensatory hypertrophy or serum LH or progesterone concentrations. In adult male rats only left-sided deafferentiation combined with left orchidectomy resulted in decreased T production, while in prepubertal male rats, only right-sided brain surgery plus left orchidectomy resulted in a significant decrease in basal testosterone secretion of the remaining testis. These findings indicate that mediobasal temporolimbic structures are involved in the neural control of gonadal functions. It appears that this lateralized mechanism is age- and sex-dependent.

Neuropathological findings in 224 patients with temporal lobe epilepsy.

During the period between 1976 and 1990, 247 patients with pharmaco-resistant complex partial seizures and a documented unilateral epileptogenic area in the mediobasal temporal lobe underwent a selective amygdalo-hippocampectomy procedure at our institution. Biopsy specimens from 224 patients (91% of the total) were available for a retrospective histopathological and immunohistochemical review. The tissue specimens of 23 patients without evidence for a macroscopic lesion have been used for neurochemical studies and could not be evaluated histopathologically. The most common temporal lobe pathology were neoplasms in 126 patients, i.e. 56%. Tumor entities observed included 23 astrocytomas (18% of all tumors), 17 gangliogliomas (13%), 15 oligodendrogliomas (12%), 15 cases of glioblastoma multiforme (12%), 13 pilocytic astrocytomas (10%), 12 oligo-astrocytomas (10%), 11 anaplastic astrocytomas (9%) and 20 tumors of various other histologies. In 23 specimens (10%), small foci of oligodendroglia-like clear cells were found. The frequent association of these foci with low-grade gliomas or neural hamartomas raises the possibility that these structures may serve as precursor lesion for neuroepithelial tumors of the temporal lobe. In 98 cases, pathological changes of non-neoplastic origin were encountered. The most common diagnoses in this group included hippocampal gliosis/sclerosis (49 cases, 22%) and vascular malformations (20 cases, 9%). Hamartomas, i.e. focal accumulations of dysplastic neuro-glial cells were diagnosed in 14 patients (6%). In only four cases have we not been able to detect any microscopic pathology. These results indicate that a high proportion of pharmaco-therapy-resistant complex-partial seizures are caused by neoplasms of the temporal lobe, some of which appear to be strikingly overrepresented in this group of patients.