Of 54 consecutive patients with multiple cranial nerve palsies in a recent prospective study from India, 20 (37%) had a cavernous sinus syndrome, with infection the next most frequent pathology. The authors note that infectious diseases predominate in the Indian subcontinent, and near one-third of cranial nerve palsies are due to tuberculous meningitis.1 Yet cavernous sinus syndrome—classically from thrombosis within the cavernous sinus but potentially from any number of pathologies related to its contents and location—is more common still, in the setting of multiple cranial nerve palsies.
The cavernous sinus (CS) is not a venous plexus but a true dural venous sinus. The dural venous sinuses are channels between the two layers of dura mater and are responsible for the venous drainage of the brain, skull, and orbit (the internal ear also). The cavernous sinus is a paired sinus situated immediately lateral to the sella turcica. It has extensions of dura forming its inferior and lateral walls and roof, rendering it septate internally, and it is bordered by the temporal bone of the skull and the sphenoid bone.2 Its central location at the base of skull, its contents, as well as its function as cerebral venous conduit, make the rather diminutive cavernous sinus an integral structure.
The 2 x 1 cm sized, blood-filled cavernous sinus contains the: internal carotid artery (carotid siphon) surrounded by sympathetic fibers, abducens nerve (CN VI), as well as the cranial nerves CN III (oculomotor nerve); IV (trochlear nerve); and two branches of the trigeminal nerve: V1 (ophthalmic branch) and V2 (maxillary branch). The cavernous sinus syndrome is characterized by edema (swelling) of the eyelids and the conjunctivae of the eyes and paralysis of the cranial nerves which course through it.
Technically, bulbar (i.e. brainstem) and pseudobulbar palsy reflect multiple cranial nerve involvement, although they are sometimes classified separately from other multiple cranial nerve palsies.
Signs of a pseudobulbar palsy – bilateral UMN IX, X, XII lesions:
- normal to increased gag reflex
- spastic tongue (small immobile) with spastic dysarthria
- increased jaw jerk
Causes of a pseudobulbar palsy – bilateral UMN IX, X, XII lesions:
- Cerebrovascular accident
- Multiple Sclerosis
- Motor Neurone Disease
Pseudobulbar palsy is a clinical syndrome of dysarthria, dysphagia, a hyperactive gag reflex and labile emotional responses. It results from upper motor neuron brainstem lesions interrupting the corticobulbar pathways on both sides. Bulbar palsy is the lower motor neuron syndrome affecting nominally the same lowermost cranial nerves (but involving the cranial nerves proper rather than the descending corticobulbar fibres that synapse at the cranial nerve nuclei). It also results in dysarthria and dysphagia, but with a decreased gag reflex and absence of emotional lability.3 Bulbar palsy can be caused by syringobulbia, as part of lateral or medial medullary syndrome, or from poliomyelitis. Progressive bulbar palsy is considered a variant form of amyotrophic lateral sclerosis (ALS). Neuro-Bechet’s syndrome and Guillain-Barre syndrome have also been reported as causing bulbar palsy.
Exceptions to the decussation rule for corticobulbar fibres: All corticobulbar fibers to the motor nucleus of the hypoglossal nerve (XII) cross to the contralateral motor nucleus and, All corticobulbar fibers to the lower half of the motor nucleus of the facial nerve (VII) cross to the lower half of the contralateral motor nucleus.
That cavernous sinus syndrome does not make my list of causes for multiple cranial nerve palsies perhaps reflects a technicality of its syndromal status—it is a constellation of symptoms and signs. Cavernous sinus syndrome is any disease process involving the CS, such as a cavernous sinus thrombosis or even caroticocavernous aneurysm. Howbeit, a cavernous sinus thrombosis itself has many potential causes.
Causes of multiple cranial nerve palsies:
- nasopharyngeal carcinoma
- chronic meningitis e.g. TB, sarcoid
- mononeuritis multiplex
- Guillain-Barre syndrome
- brainstem infarction
- Arnold-Chiari malformation
- trauma
- Paget’s disease
In a 2005 Californian-based personal case series review of 979 unselected inpatients with simultaneous or serial involvement of two or more different cranial nerves, tumour, including brainstem tumour, was responsible for 30% of cases (n = 305). Schwannomas (5.4%) were most common, followed by metastases (5%) and meningiomas (4.2%). Lymphoma (2.9%) was more common than nasopharyngeal carcinoma (2.7%).5 In this series, cavernous sinus thrombosis was the cause of 5% of cases of multiple cranial nerve palsies. The proportion of multiple cranial nerve palsies caused by a cavernous sinus syndrome, however, is not clear from the data.
A disease may involve homologous nerves on both sides, such as bilateral facial palsy, or different nerves on the same or opposite sides. In some conditions, a cluster of nerves is involved in a discrete anatomical region. The progression may follow some anatomical pattern or appear capricious. Multiple CNs may be affected from the outset, or the process may begin with one nerve and progress to involve others. Pain may or may not be present.4
References
- Mehta MM, Garg RK, Rizvi I, Verma R, Goel MM, Malhotra HS, Malhotra KP, Kumar N, Uniyal R, Pandey S, Sharma PK. “The Multiple Cranial Nerve Palsies: A Prospective Observational Study.” Neurol India. 2020 May-Jun;68(3):630-635. doi: 10.4103/0028-3886.289003. PMID: 32643676.
- Kuybu O, Dossani RH. “Cavernous Sinus Syndromes.” [Updated 2020 Jul 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532976/.
- Bell, Daniel J.; and Alexandra Stanislavsky, Alexandra et al. Pseudobulbar palsy | Radiology Reference Article | Radiopaedia.org.
- Brainstem and Multiple Cranial Nerve Syndromes | Neupsy Key.
- Keane JR. “Multiple Cranial Nerve Palsies: Analysis of 979 Cases.” Arch Neurol. 2005;62(11):1714–1717. doi:10.1001/archneur.62.11.1714.
