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Dolichoectasia of the Intra-cavernous Internal Carotid Artery:
a rare etiology of recurrent abducens palsy
Carla B. Engelke, OD, FAAO
Abstract:
Dolichoectasia of the intra-cavernous internal carotid artery (ICA) can elicit neuroophthalmological sequelae, which rarely presents as isolated, recurrent abducens palsy. It is rare
for cavernous sinus pathology to give rise to isolated abducens palsy, however when present it
may be the only indicator of intra-cavernous disease.
*Case History: 60 year old Hispanic male
*CC: diplopia worsening on right gaze for 3 months
*Ocular History: previous episode of diplopia 9 months earlier that spontaneously
resolved after one month; no glaucoma, surgery, injury
*Medical History: Hypertension, Hypercholesterol
*Medications: HCTZ 25mg qd, Lovastin 40 mg qd, Atenolol 25mg qd
*Pertinent findings:
*Clinical:
*BCVA 20/20 OD, OS
*Pupils equal, round, reactive to light; no APD
*EOM: Abduction deficit OD
*CTsc: 15^pd esotropia @ 6m (primary gaze)
18^pd esotropia @ 6m (right gaze)
*Optic Nerve Head: 0.35R with distinct margins OD, OS
*Physical:
*BP: 141/96
Pulse: 85
*SITA STD 24-2:
*Normal field OD, OS
*Laboratory studies:
*ESR, CRP, fasting glucose, platelet count: WNL
*Radiology studies:
*CT without contrast: Unremarkable
*MRI with contrast: Fusiform enlargement of intracavernous portion of
right ICA
*Cerebral Angiography & MRA:
Carotid siphon portion of ICA demonstrates ectasia—
intracavernous ICA enlarged with no
focal aneurysmal dilation visualized
*Differential Diagnosis:
*Primary/leading: Acquired CN VI palsy secondary to:
*Compressive lesion:
--Dolichoectasia
--Aneurysm
--Space occupying
--Increased intracranial pressure
*Secondary differentials:
*Infarction: micro-vascular or CVA
*Trauma
*Inflammation
*Infection
*Neoplastic infiltration
*Multiple sclerosis
*Idiopathic
*Imposters: Duane’s retraction syndrome, thyroid related orbitopathy, orbital
inflammatory disease (pseudotumor), myasthenia gravis, & spasm of
near reflex
*Diagnosis and discussion:
*Unlike CN III, IV, & V, which run in the lateral wall of the sinus, the CN VI
runs medially in close proximity to the ICA. Due to this anatomical arrangement,
the CN VI is more susceptible to compromise if the ICA is enlarged. Typically
cavernous sinus pathology causes multiple cranial nerve palsies with pupillary
involvement; rarely however, an isolated CN VI palsy can be an early indicator
of cavernous sinus pathology. CN VI palsies are commonly attributed to
vasculopathic or idiopathic origin in the aging adult; however, in cases when the
palsy is reoccurring, a compressive lesion or ectasia must be ruled out.
*Dolichoectasia as demonstrated in this case signifies the pathological enlargement of a
vessel along its length as opposed to an aneurysm which is a focal out-pouching and/or
weakening of the vessel wall. The current theory of its formation in older adults is
based on the effect of chronic arterial hypertension, arteriosclerosis, and atheromatous
plaque formation damaging the elastic lamina of the vessel wall and subsequently
causing it to loose its elasticity and enlarge. Based on histological evidence,
dolichoectatic vessels demonstrate abnormal connective tissue composition with
absence or fragmentation of the internal elastic lamina, thickened media with fibrinoid
material deposition, and attenuated muscularis tissue. In conjuction with aging and
hypertension, depletion of elastic collagen fibers and deficiency of smooth muscle
reticular fibers decreases the vessel wall’s ability to repair itself. This leads to a
progressive diliatation which in turn can act as a space-occupying lesion.
*The isolated, recurrent right CN VI palsy was attributed to dolichoectasia of the right
internal carotid artery because of the lesion discovered on MRI, MRA, & cerebral
angiography and its proximity to CN VI within the cavernous sinus. HTN was also
thought to be a secondary aggravating factor in contributing to the CN VI palsy.
*This patient marks the third documented case of a unilateral CN VI to be associated
with dolichoectasia; there has been one reported case of bilateral involvement.
*Additionally, this case serves as a review of when it is indicated for an optometrist to
order imaging studies as well as which studies are the most appropriate to order (i.e.
MRI vs CT scan & MRA vs cerebral angiography)
*Treatment and management:
*Treatment involved patching OD for comfort, monthly follow-up in the eye clinic and
concurrent co-management with the patient’s primary care physician, interventional
radiology, & neurology/neuro-surgery. At the second monthly follow-up, the diplopia
had resolved. Surgery was not indicated secondary to the location of the lesion and risk
of mortality. Careful observation combined with strict HTN control was deemed the
best long-term course of treatment.
*Conclusion:
*Dolichoectasia of the intra-cavernous ICA is a rare etiology of isolated, recurrent CN VI
palsy. Imaging studies should be performed on patients with recurrent diplopia in order
to rule out dolichoectatic and/or aneurysmal vessel changes as the underlying etiology.
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