Case 17 - Slurred speech
What is the lesion?
A huge range of diagnostic possibilities exists for hypoglossal palsy (table 3). Some have specific features that might provide clues, and obviously localisation to a given site helps when considering causes, given the tissues involved. The 2024 review in Biomedicines by Wegiel et al is well worth looking at.
A high number of hypoglossal palsies end up with a label of ‘idiopathic’ – but this should only be accepted after a reasonable hunt for important causes. Note that malignancy (of many types) appears at any location – arguably, more than any other cranial nerve, hypoglossal palsy is associated with cancer, so the index of suspicion must be high. This patient has previous rectal cancer, and this casts an immediate and ominous shadow over the case.
A medullary lesion of any kind might involve XII and other structures - as before, the best examples are medial medullary infarction and syringobulbia. Fourth ventricle tumours such as ependymomas could potentially compromise the nerve but this is unusual as a presentation (it is reported post-operatively however). Demyelination/inflammation in the upper dorsal medulla is not common in contrast to other sites such as the pons (where the trigeminal pathways and medial longitudinal fasciculus are frequent targets).
In the subarachnoid space adjacent to the medulla, XII runs near the vasculature; aneurysms or dolichoectatic dilatation of vessels could compress and disrupt the nerve. Meningeal processes (e.g. cancerous invasion, inflammation or infection) can also produce lower cranial neuropathies.
The skull base is a major site for tumours and no hypoglossal palsy should ever be labelled as ‘idiopathic’ before this is ruled out. Many exist, including metastasis as well as primary bone tumours such as chondosarcoma, and they may or may not produce headache. Other pathologies at this site include arteriovenous fistula and bone fractures.
In the initial parts of XII travelling in the neck, pathologies in or around the upper cervical spine, the jugular foramen, or at the carotid sheath are important causes. Cervical fractures can compromise XII, whether by direct displacement of bone onto the nerve or disruption of the soft tissues nearby. A range of jugular foramen or nearby lesions can compromise the lower cranial nerves - XII is not within the jugular foramen but joins the other lower nerves (IX-XI) after they pass through it.
Carotid dissection is a serious condition capable of devastating effects, mainly via embolic infarction of the brain (middle and/or anterior cerebral artery territories) – but additional features can include compromise of lower cranial nerves and Horner’s if the sympathetic chain is affected. Any hypoglossal palsy with neck pain requires angiography to exclude this – as identifying it can help prevent stroke.
Other pathologies can affect the carotid sheath, including malignancy (e.g. lymphoma).
The distal XII runs in the space below the tongue, and infectious or malignant processes here (e.g. squamous cell cancer) are major concerns.
In summary there is a broad range of possibilities, but cancer - whether near the medulla, in the meninges, the skull base, or the neck and sublingual zones - clearly is a concern in this case.
Clinical formulation