Introduction
Glucose Transporter Type I Deficiency Syndrome (
GLUT
1
DS
) classical symptoms are seizures, involuntary movements, and cognitive impairment but so far the literature has not devoted much attention to the last.
Methods
In our retrospective study involving 25 patients with established
GLUT
1
DS
diagnosis, we describe the cognitive impairment of these patients in detail and their response to the ketogenic diet in terms of cognitive improvement.
Results
We outlined a specific cognitive profile where performance skills were more affected than verbal ones, with prominent deficiencies in visuospatial and visuomotor abilities. We demonstrated the efficacy of ketogenic diet (
KD
) on cognitive outcome, with particular improvement tin total and verbal
IQ
; we found that timing of
KD
introduction was inversely related to
IQ
outcome: the later the starting of
KD
, the lower the
IQ
, more notable nonverbal scale (verbal
IQ
correlation coefficient −0.634,
p
‐value = 0.015). We found a significant direct correlation between cognition and
CSF
/blood glucose ratio values: the higher the ratio, the better the cognitive improvement in response to diet (from T0–baseline evaluation to T1 on average 18 months after introduction of
KD
‐:
TIQ
correlation coefficient 0.592,
p
‐value = 0.26;
VIQ
correlation coefficient 0.555,
p
‐value = 0.039). Finally, we demonstrated that a longer duration of treatment is necessary to find an improvement in patients with “severely low ratio.”
Conclusion
Our results were consistent with the hypothesis that timing of the diet introduction is a predictive factor of cognitive outcome in these patients, confirming that earlier initiation of the diet may prevent the onset of all
GLUT
1
DS
symptoms: epilepsy, movement disorders, and cognitive impairment.