Evidence for normal letter-sound integration, but altered language pathways in a case of recovered Landau-Kleffner Syndrome

Landau-Kleffner Syndrome (LKS) is a rare form of acquired aphasia in children, characterized by epileptic discharges, which occur mostly during sleep. After normal speech and language development, aphasia develops between the ages of 3-7 years in a period ranging from days to months. The epileptic discharges usually disappear after reaching adulthood, but language outcomes are usually poor if no treatment focused on restoration of (non-) verbal communication is given. Patients often appear deaf-mute, but sign language, as part of the treatment, may lead to recovery of communication. The neural mechanisms underlying poor language outcomes in LKS are not yet understood. In this detailed functional MRI study of a recovered LKS patient - that is, a patient no longer suffering from epileptic discharges, audiovisual multi-sensory processing was investigated, since LKS patients are often proficient in reading, but not in speech perception. In the recovered LKS patient a large difference in the neural activation to auditory stimuli was found in the left versus the right auditory cortex, which cannot be attributed to hearing loss. Compared to healthy proficient readers investigated earlier with the same fMRI experiment, the patient demonstrated normal letter-sound integration in the superior temporal gyrus as demonstrated by the multi-sensory interaction index, indicating intact STG function. Diffusion Tensor Imaging (DTI) based fiber tracking in the LKS patient showed fibers originating from Heschl's gyrus that seem to be left-right inverted with respect to HG fiber pattern described in the literature for healthy controls. In the patient, in both hemispheres we found arcuate fibers projecting from (homologues of) Broca's to Wernicke's areas, and a lack of fibers from arcuate left inferior parietal and sylvian areas reported in healthy subjects. We observed short arcuate segments in the right hemisphere. Although speculative, our results suggest intact temporal lobe processing but an altered temporal to frontal connectivity. The altered connectivity might explain observed short-term verbal memory problems, disturbed (speech) sound-motor interaction and online feedback of speech and might be one of the neuronal factors underlying LKS.

Pediatric focal epilepsy syndromes

Benign epilepsy with centrotemporal spikes, early-onset childhood occipital epilepsy (Panayiotopoulos syndrome [PS]) and late-onset childhood occipital epilepsy (Gastaut type [LOCE-G]) are the principal pediatric focal epilepsy syndromes. They share major common characteristics: the appearance and resolution of electroclinical features are age related, there is a strong genetic predisposition, the clinical course is often mild with infrequent and easy to control seizures, interictal epileptiform activity is disproportionately abundant when compared with the clinical correlate, and tends to potentiate and generalize during sleep. In this review, we outline the relevant pathophysiology underlying this electroclinical spectrum. Then, the initial description of individual syndromes is followed by a summary of overlapping features and intermediate presentations that question the boundaries between these entities and provide the basis for the concept of a childhood seizure susceptibility syndrome. Additionally, we outline the main features of the related epileptic encephalopathies. An outlook on potential future lines of research completes this review.

Landau-Kleffner syndrome: a rare auditory processing disorder series of cases and review of the literature

OBJECTIVE

To describe the clinical presentation and treatment of 3 children with an Auditory Processing Disorder with an identifiable neurological cause: Landau-Kleffner syndrome. This classical syndrome is well recognized in pediatric neurology but the diagnosis is less well known to Pediatric Otolaryngology, Speech Language Pathology and Audiology services.

METHODS

Retrospective chart review of three patients with Landau-Kleffner syndrome.

RESULTS

In all cases, pharmacological intervention led to clinical and electroencephalographic improvement, but all patients had long-term difficulty with understanding sounds in a noisy environment. Magnetic Resonance Imaging (MRI) of the brain was normal in all three patients. Their language disturbance improved over time. Speech language intervention was helpful in addressing communication difficulties arising from the auditory processing/receptive and expressive language disorder.

CONCLUSION

A multidisciplinary assessment is the key for early diagnosis, treatment and follow-up in patients with this syndrome.