The circuit of Papez in mesial temporal sclerosis: MRI

Abstract

We looked at abnormalities in the circuit of Papez in patients with the mesial temporal sclerosis (MTS). We reviewed the MRI studies of 15 patients with probable MTS, seeking changes in the fornix, mamillary body, mamillothalamic tract, thalamus and cingulate and parahippocampal gyri. We correlated any abnormalities with each other and with clinical severity. Atrophy and/or signal change in one or more structures in the circuit of Papez were found in five patients. They involved the parahippocampal gyri in all five, the fornices in four, mamillary bodies in three, the thalamus in two and the cingulate gyrus in one. Changes in the fornix, mamillary body, thalamus or cingulate gyrus were always accompanied by hippocampal and parahippocampal atrophy. The patients with abnormalities of the circuit of Papez did not have more severe epilepsy than those without. Changes in the parahippocampal gyrus, including the entorhinal cortex and subiculum, in which forniceal fibres originate, may be crucial in causing abnormalities more distally in the circuit.

Placement of Deep Brain Electrodes in the Dog Using the Brainsight Frameless Stereotactic System: A Pilot Feasibility Study

“…This structure then completes the circuit by returning to the hippocampus. Atrophy or sclerosis of any structures within the circuit has been known to cause epilepsy, as occurs with mesial temporal sclerosis 41. Although mesial temporal sclerosis has yet to be described in dogs, the importance of the Papez circuit in the propagation of seizure activity suggests that it remains an important target for the treatment of epilepsy in dogs.…”

Deep Brain Stimulation for Epilepsy

“…Radiologic alterations have been noted in structures within the classic circuit of Papez in mesial temporal sclerosis, as well as other forms of epilepsy. 27 Thus, it is conceivable that DBS of structures within this circuit may result in direct anterograde cortical stimulation. The ANT is an appealing target because of its relatively small size and projections to limbic structures, ultimately affecting wide regions of neocortex.…”

“…26,27,73 Subacute hippocampal stimulation (HS) using bilateral depth electrodes or unilateral electrode grids abolished complex partial and secondarily generalized tonic-clonic seizures and significantly decreased the number of interictal EEG spikes at the focus in 7 of 10 patients with intractable temporal lobe seizures. 74 A subsequent study of chronic HS by the same group in three patients demonstrated persistently blocked epileptogenesis with no negative effect on shortterm memory.…”

Deep Brain Stimulation for the Treatment of Epilepsy: Circuits, Targets, and Trials

“…The networks incorporating these pathways-such as the cortical-striatal-thalamic network [16][17][18] and the limbic circuit of Papez ( Fig. 1) [19,20]-provide nodes at which neuromodulatory tools such as electrical stimulation have the potential to regulate the flow of neural information, including pathological signals mediating seizure propagation.…”

“…Originally characterized for its role in mediating emotions, more recently this circuit has been associated with memory, as well as the generation and propagation of limbic (e.g., mesial temporal lobe) seizures [19,21]. The circuit originates from the hippocampus and subiculum, projects via the fornix to the mammillary body, then via the mammilothalamic tract to the anterior nucleus of the thalamus (ANT) (Fig.…”