Canalis nervi hypoglossi

Hypoglossusparese

links als Folge einer osteoblastischen Metastasierung um das Foramen nervi hypoglossi bei Prostatakarzinom.

Persistent

idiopathic unilateral isolated hypoglossal nerve palsy – a report of two cases. a Right-sided atrophy along with tongue deviation 7 months after onset of symptoms. b Cisternal segment of the right hypoglossal nerve (HN) on 3D constructive interference in steady state (CISS) magnetic resonance imaging (MRI) showing normal appearance (white arrow). c Normal morphology of the skull base segment of the right HN inside of the right hypoglossal canal (HC) on 3D T1-weighted contrast enhanced (CE) MRI. The HN is of hypointense signal (white arrow), while the surrounding venous plexus shows prominent CE. d Axial computed tomography scan of the skull base demonstrating a normally appearing HC (white arrow). e Head and neck T1-weighted MRI demonstrates fatty infiltration and atrophy of the right half of the tongue due to chronic muscle denervation (white arrow)

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Occipita

bone. Inner surface.

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The hypoglossal canal is located between the occipital condyle and jugular tubercle and runs obliquely forwards (posteromedial to anterolateral) allowing the hypoglossal nerve to exit the posterior cranial fossa.

Its proximal portion is often divided by a fibrous (sometimes ossified) septum, which separates the two roots of the hypoglossal nerve (these have formed by the convergence of numerous rootlets). These roots merge within the canal and a single nerve emerges.

Cross-sectional anatomy

The hypoglossal canal is most easily identified on axial or coronal images through the occipital condyles, where it can be seen passing anterolaterally from the posterior fossa into the upper neck.

On coronal imaging, the jugular tubercle appears beak-like extending over the hypoglossal canal. Combined with occipital condyle the coronal appearance is reminiscent of an eagle seen in profile, making this a convenient landmark .