Rebecca Spiegel, MD, MA
Edward Y. Lee, MD, MPH
from the Department of Neurology, Albert Einstein College of
Medicine, Bronx, NY.
A 6-year-old boy with a 5-year history of intractable complex
partial seizure was referred by his neurologist for a presurgical
evaluation of a brain locus that may have triggered the seizures.
The seizures were described as starting with vocalizations that
would quickly convert to convulsions of all four extremities.
Afterward, the patient would become aphasic or dysarthric for
approximately 1 minute; then the patient would become sleepy.
The patient had been on multiple seizure medications in the
past. All of the seizure medications had proven to be ineffective
in completely controlling his seizures. On average, the seizure
frequency was 5 to 8 times per month. His physical examination was
significant for fairly marked hyperactivity and compulsive
behavior, such as repeated counting. He was also found to have
mildly reduced language fiuency as compared with that expected for
his age. The rest of his examination was unremarkable. The
patient's presurgical work-up included an electroencephalography
(EEG), which revealed intermittent left temporal slowing,
suggestive of either a postictal state or a structural abnormality
in this region. In addition, the patient underwent magnetic
resonance imaging (MRI) (Figure 1) and positron emission tomography
(PET) (Figures 2 and 3).
MRI of the brain shows brain parenchymal volume loss of the left
hippocampus, which is compatible with mesial temporal sclerosis
(Figure 1). Axial and coronal brain PET shows decreased F-18
fiuorodeoxyglucose (FDG) uptake in the left temporal lobe, which is
consistent with the MRI finding of left-sided mesial temporal
sclerosis (Figures 2 and 3).
Left mesial temporal sclerosis (MTS)
While MTS is the most common symptomatic pathologic entity in
adult and adolescent patients with seizures of temporal lobe
origin, it is considered to be a rare pathologic finding among
infants and young children.
The etiology of MTS is still not fully understood. However, there
is now considerable evidence, from both animal and clinical
studies, that has shown that MTS is not only the cause of seizures,
but is also the result of seizures.
Animal studies suggest that the mechanism by which seizures can
cause MTS is through the release of excitatory amino acids,
These excitatory amino acids lead to prolonged neuronal
depolarization and result in the entry of cytotoxic amounts of
calcium, which can eventually lead to sclerosis. Clinical studies
also suggest that prolonged seizures are a risk factor for MTS and
that a period of time is required for the lesions to fully develop.
Clinical presentation of MTS in adults and adolescents is
characterized by auras that often involve visceral sensation,
motionless stare, loss of awareness, and oral alimentary
Infants typically do not have any identifiable auras, present with
seizures that are of longer duration (>1 minute), and have more
prominent convulsive activity. Moreover, infants predominately
present with behavioral arrest with possible impairment of
consciousness. Their automatism is mostly discrete and
MRI is the radiological investigation of choice for the
evaluation of patients with MTS, since it can identify structural
However, other MR techniques, such as magnetic resonance
spectroscopy (MRS) and functional MRI (fMRI) are also being
increasingly used in the diagnosis of MTS. MR spectroscopy can
detect metabolic abnormalities, while fMRI allows for the
noninvasive evaluation and localization of cognitive, motor, and
sensory deficits that are associated with MTS. Also, intraoperative
MRI-based image-guided systems are now used as an adjunct in the
surgical treatment of MTS for better anatomic localization.
Along with MRI, the use of PET scans with FDG is also
well-established for the diagnosis of MTS. In the interictal state,
the epileptogenic temporal lobe indicates decreased glucose
metabolism in approximately 80% of these patients. Moreover, PET
scans may be a reliable indicator of clinical outcome postsurgery;
the presence of a hypometabolic temporal lobe is a favorable
Antiepileptic drug treatment for patients with MTS is effective
in the suppression of secondarily generalized seizures. However,
50% of patients continue to have partial attacks. With combined use
of MRI, PET, and video-EEG, we can properly select patients who can
benefit from anterior temporal lobe resection. In such patients,
complete seizure control is achieved in >80% of cases.
Patients who had an earlier age of onset and a low number of
previously used antiepileptic agents have an overall better outcome
Mesial temporal lobe sclerosis contributes to a significantly
compromised quality of life of many patients. Antiepileptic agents
offer complete seizure control in only a minority of these
patients. However, with the aid of MRI and PET scans, patients can
now be selected to undergo anterior temporal lobe resection, a
procedure that leads to seizure control in a majority of