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Meningitis and the evolution of dominance of righthandedness
P Bol1, J Scheirs, L Spanjaard
1Netherlands' Reference Laboratory for Bacterial Meningitis (WHO Collaborative Centre) of the Academic Medical Centre, Amsterdam.
Abstract:
In bacterial meningitis, forced deviation of the head and/or the eyes towards either the left or the right side reflects an ipsilateral focal inflammation of the brain. Also, the symptom of forced deviation is associated with a high fatality and sequelae rate. In this study it was observed that, among 2124 Dutch patients with bacterial meningitis, forced deviation was significantly more often to the right than to the left. Because the right hemisphere is dominant for motor functions in natural lefthanders, it was concluded that bacterial meningitis might have been a selection mechanism favouring the evolution of a dominance of righthandedness.
Insights
Bacterial meningitis causes head and eye deviation, often to the right. This study suggests this pattern may have driven the evolution of right-handedness dominance.
Area of Science:
- Neurology
- Infectious Diseases
- Evolutionary Biology
Background:
- Bacterial meningitis can cause focal brain inflammation, leading to forced head and eye deviation.
- This neurological symptom is linked to high fatality and long-term sequelae rates.
Purpose of the Study:
- To investigate the directional preference of forced deviation in bacterial meningitis patients.
- To explore the potential evolutionary implications of observed deviation patterns on handedness.
Main Methods:
- Analysis of clinical data from 2124 Dutch patients diagnosed with bacterial meningitis.
- Statistical comparison of the frequency of leftward versus rightward forced deviation.
Main Results:
- Forced deviation was observed significantly more frequently to the right than to the left in the studied patient cohort.
- This finding was correlated with the known dominance of the right hemisphere for motor control in left-handed individuals.
Conclusions:
- Bacterial meningitis-induced brain inflammation may exhibit a directional bias.
- This directional bias could have acted as a selective pressure favoring the evolution of right-handedness dominance in the human population.