Post by neurology admin on Jun 27, 2012 2:37:50 GMT -5
Lower cranial nerve palsies in various combinations
involving the hypoglossal, glossopharyngeal,
vagal, and the accessory nerves occur in
internal carotid artery (ICA) dissection.1¨C8 17
The hypoglossal nerve (cn-XII) is most often
affected. It is suggested that the close proximity
of these nerves to the cervical ICA may subject
them to mechanical injury either by the
expansion of the dissected artery or by aneurysm
formation.1 3 9 10 Dissection of the ICA
may cause transient or permanent disruption of
the blood supply to these cranial nerves.6 11
Therefore, cranial nerve injuries may result from
¡°mechanical, embolic, or haemodynamic¡± processes
caused by ICA dissection.6 This hypothesis
is supported by anatomical and clinical findings.
2 6 12 Each half of the genioglossus muscle
that protrudes the tongue is innervated by contralateral
corticobulbar (crossed) fibres whereas
all other intrinsic and extrinsic tongue muscles
that move the tongue within the mouth in all
directions have bilateral cortical innervation.13 14
Unilateral cortical lesion in the topography representing
the tongue may therefore cause
contralateral genioglossus muscle weakness,
resulting in deviation of the protruded tongue
away from the side of the cortical lesion. By contrast,
cn-XII injury causes ipsilateral genioglossus
muscle weakness; hence the protruded
tongue deviates to the side of the injured nerve.
www.ncbi.nlm.nih.gov/pmc/articles/PMC1737417/pdf/v070p00806.pdf
involving the hypoglossal, glossopharyngeal,
vagal, and the accessory nerves occur in
internal carotid artery (ICA) dissection.1¨C8 17
The hypoglossal nerve (cn-XII) is most often
affected. It is suggested that the close proximity
of these nerves to the cervical ICA may subject
them to mechanical injury either by the
expansion of the dissected artery or by aneurysm
formation.1 3 9 10 Dissection of the ICA
may cause transient or permanent disruption of
the blood supply to these cranial nerves.6 11
Therefore, cranial nerve injuries may result from
¡°mechanical, embolic, or haemodynamic¡± processes
caused by ICA dissection.6 This hypothesis
is supported by anatomical and clinical findings.
2 6 12 Each half of the genioglossus muscle
that protrudes the tongue is innervated by contralateral
corticobulbar (crossed) fibres whereas
all other intrinsic and extrinsic tongue muscles
that move the tongue within the mouth in all
directions have bilateral cortical innervation.13 14
Unilateral cortical lesion in the topography representing
the tongue may therefore cause
contralateral genioglossus muscle weakness,
resulting in deviation of the protruded tongue
away from the side of the cortical lesion. By contrast,
cn-XII injury causes ipsilateral genioglossus
muscle weakness; hence the protruded
tongue deviates to the side of the injured nerve.
www.ncbi.nlm.nih.gov/pmc/articles/PMC1737417/pdf/v070p00806.pdf