Parkinson sign (cavernous sinus localization sign)

Key Points at a Glance

Key Points of This Disease

• Parkinson sign is a clinical sign consisting of isolated abducens nerve (CN VI) palsy combined with ipsilateral postganglionic Horner syndrome.
• This sign is unrelated to Parkinson disease (dopaminergic neurodegeneration of the basal ganglia); caution is needed to avoid confusion of the names.
• The anatomical basis of this sign is the close proximity of the sympathetic chain and the abducens nerve in the posterior cavernous sinus.
• It has high diagnostic value in localizing the lesion to the ipsilateral cavernous sinus.
• The main causes are space-occupying lesions, vascular lesions, and inflammatory diseases, all of which require early identification of the cause and etiology-specific treatment.
• The apraclonidine eye drop test is the most practical for confirming Horner syndrome, with a high sensitivity of 88–100%.

1. What is Parkinson sign?

Parkinson sign is a clinical sign in which isolated sixth cranial nerve palsy (abducens nerve palsy) is combined with ipsilateral postganglionic Horner syndrome. This combination has high localizing diagnostic value, suggesting a lesion in the posterior cavernous sinus ¹.

The cavernous sinus is located superior to the sphenoid sinus and lateral to the sella turcica, and contains the oculomotor nerve (III), trochlear nerve (IV), abducens nerve (VI), trigeminal nerve (V1, V2), ocular sympathetic nerve, and internal carotid artery ². In the posterior cavernous sinus, the ocular sympathetic chain leaves the internal carotid artery and runs in close proximity to the abducens nerve ¹³. Due to this anatomical relationship, compression or inflammation at this site can simultaneously damage both structures.

Note that “Parkinson’s disease” is a movement disorder caused by dopaminergic neurodegeneration in the substantia nigra of the midbrain, and is a completely different disease concept from Parkinson’s sign.

Q Is there a relationship between Parkinson's sign and Parkinson's disease?

A

They are unrelated. Parkinson’s sign is a combination of abducens nerve palsy due to a lesion in the cavernous sinus and Horner syndrome, and although the name is similar to Parkinson’s disease (a movement disorder caused by dopaminergic neurodegeneration in the substantia nigra), the pathology, cause, and treatment are all different.

2. Main symptoms and clinical findings

Subjective symptoms

• Horizontal diplopia: Due to abduction impairment. It worsens when looking toward the affected eye, and a face turn (compensatory head posture) toward the affected side occurs to reduce diplopia.
• Headache: May involve pain around the orbit or occipital region.
• Eye pain or retro-orbital pressure: Caused by irritation from lesions in the cavernous sinus.
• Blurred vision or decreased visual acuity: Occurs when ptosis is severe.

Clinical Findings (Findings Confirmed by Physician Examination)

• Miosis: Anisocoria more noticeable in dim light. Pupillary light reflex is normal, but dilation after constriction is delayed. May appear as enophthalmos, but this is due to narrowing of the palpebral fissure; the actual position of the eye is unchanged.
• Partial ptosis: Drooping of the upper and lower eyelids on the same side as miosis. Presents with narrowing of the palpebral fissure characteristic of Horner syndrome.
• Facial anhidrosis: Impaired sweating on the same side of the face.
• Inability to abduct the affected eye: Paralytic esotropia due to lateral rectus dysfunction. Diplopia worsens on abduction.

3. Causes and Risk Factors

The causes of Parkinson’s signs are diverse and involve the following lesions occurring in or posterior to the cavernous sinus.

Space-occupying lesions

Meningioma and schwannoma: Benign to malignant tumors arising in the cavernous sinus.

Lymphoma/metastasis: Breast cancer, prostate cancer, etc., may metastasize to the orbit, cavernous sinus, or meninges, causing isolated abducens nerve palsy.

Vascular lesions

Internal carotid artery (ICA) dissection/aneurysm: Aneurysm or dissection of the ICA within the cavernous sinus compresses the nerve.

Internal carotid artery thrombosis: Venous thrombosis damages the sympathetic and abducens nerves within the cavernous sinus.

Inflammatory and other

Tolosa-Hunt syndrome: Granulomatous inflammation within the cavernous sinus. Often responsive to steroid therapy.

Giant cell arteritis / trauma: Ischemic damage due to vasculitis, or damage from direct trauma.

Risk factors

• Smoking: Increases the risk of vascular lesions.
• Long-standing hypertension / diabetes: The most common risk factors for ischemic abducens nerve palsy (vascular etiology). In patients aged 50 years or older, ischemic etiology is predominant⁴.
• Advanced age: Vascular risk increases with age.
• Family history of malignancy or vascular disease
• Hypercoagulable state

Prevention and Daily Care

Proper management of hypertension and diabetes, along with smoking cessation, can help prevent ischemic abducens nerve palsy. Regular health check-ups to monitor blood pressure and blood glucose levels are recommended; consult a physician if abnormal values persist. If sudden double vision, eye pain, or headache occurs, promptly see an ophthalmologist or neurologist.

Q Are all causes of Parkinsonian signs serious diseases?

A

Not necessarily. Conditions range from Tolosa-Hunt syndrome, which improves rapidly with steroid therapy, to malignant tumors or internal carotid artery aneurysms requiring emergency treatment. In all cases, identifying the cause determines the treatment strategy, so early investigation is important.

4. Diagnosis and Examination Methods

Clinical Diagnosis

The diagnosis of Horner syndrome is based on a combination of the following findings.

1. Anisocoria that is more pronounced in dim light (identifying the miotic side)
2. Partial ptosis on the same side as the miosis
3. Isolated ipsilateral abducens nerve palsy (lateral rectus palsy)

If a third-order (postganglionic) Horner syndrome is confirmed with ipsilateral abducens nerve palsy, the lesion can be localized to the ipsilateral posterior cavernous sinus.

Pharmacological Testing (Confirmation and Localization of Horner Syndrome)

Three types of eye drop tests are used to confirm the presence of Horner syndrome and localize the lesion.

Test	Principle	Interpretation
Apraclonidine eye drop test	Denervation supersensitivity causes α₁ stimulation to dilate the miotic pupil	Reversal of anisocoria → positive for Horner syndrome
Cocaine eye drop test	Proof of sympathetic denervation	Miotic side does not dilate → Horner syndrome positive
Hydroxyamphetamine eye drop test	In postganglionic lesions, dilation is impossible due to neurotransmitter depletion	Miotic side does not dilate → postganglionic confirmed

When apraclonidine is instilled in both eyes and observed after 30–45 minutes, the healthy eye does not develop mydriasis, but the affected eye dilates and ptosis improves. Cocaine and tyramine are difficult to obtain, so the apraclonidine test is the most practical (sensitivity 88–100%) ⁵.

Imaging and Blood Tests

• Brain MRI/MRA: Evaluate lesions at the skull base including the cavernous sinus. Contrast-enhanced MRI is useful for identifying internal carotid artery aneurysm, dissection, tumor, or inflammation.
• ESR/CRP: Evaluation for giant cell arteritis. In elderly patients with temporal tenderness or jaw claudication, perform urgent measurement; if positive, perform temporal artery biopsy.
• CBC (Complete Blood Count): Evaluation for hematologic malignancies.

Differential Diagnosis

A pontine lesion can also affect both the descending sympathetic chain and the abducens nerve. However, pontine lesions usually also involve the facial nerve, and the resulting Horner syndrome is first-order (central), so the hydroxyamphetamine test shows dilation on the miotic side, confirming that it is not postganglionic Horner syndrome. In this case, Parkinsonian signs are ruled out.

Within the cavernous sinus, the oculomotor nerve (III), trochlear nerve (IV), and trigeminal nerve (V1) also run, and if these are also affected, it goes beyond the scope of Parkinsonian signs and should be evaluated as a broader cavernous sinus syndrome.

Q How is the apraclonidine eye drop test performed?

A

Apraclonidine (1% or 0.5%) is instilled in both eyes, and pupil size and eyelid position are observed after 30 to 45 minutes. In Horner syndrome, due to denervation supersensitivity, the pupil on the miotic side dilates, reversing anisocoria, and ptosis improves. Sensitivity is reported to be 88–100%, making it the most practical test to replace cocaine, which is difficult to obtain.

5. Standard Treatment

There is no specific treatment for Parkinsonian signs. Treatment is directed at the identified underlying disease (etiology).

Treatment by Etiology

• Space-occupying lesions (tumors): Combination of surgical resection, radiation therapy, and chemotherapy.
• Internal carotid artery aneurysm/dissection: Endovascular treatment (coil embolization, stent placement) or surgical clipping.
• Tolosa-Hunt syndrome: Steroid therapy (systemic administration of corticosteroids) is first-line. Pain often improves within 1–2 days of starting treatment, followed by improvement of ocular motor deficits ⁶.
• Giant cell arteritis: Prompt high-dose steroid therapy is required. Delay in treatment can lead to vision loss, requiring urgent management.
• Cavernous sinus thrombosis (infectious): If systemic symptoms are present, hospitalize and administer broad-spectrum intravenous antibiotics. Depending on the source of infection, consultation with otorhinolaryngology and neurosurgery, and emergency surgical drainage may be necessary.

Symptomatic treatment for abducens nerve palsy

In ischemic cases (due to hypertension or diabetes), spontaneous improvement can be expected, so conservative observation with vitamins and circulation-improving drugs is recommended for about 6 months. Prism glasses are effective for diplopia during this period.

If improvement is insufficient after 6 months, extraocular muscle surgery is considered. In addition to horizontal muscle recession/resection, muscle transposition (full tendon transposition) using the superior and inferior rectus muscles is used for severe palsy, and good ocular alignment improvement has been confirmed.

Precautions in treatment

Administering steroids before completing the etiological workup may temporarily improve neoplastic diseases (such as lymphoma) and delay diagnosis. Steroid administration should be carefully considered when the cause is not yet confirmed.

Q Can diplopia due to abducens nerve palsy be cured?

A

In cases of ischemic etiology, spontaneous improvement often occurs within 3 to 6 months. For other causes, treatment of the underlying disease is the main approach. If no improvement is seen, consider prism glasses to reduce diplopia or extraocular muscle surgery (recession/resection or transposition).

6. Pathophysiology and Detailed Mechanism

Course of the Sympathetic Chain (Oculosympathetic Pathway)

The oculosympathetic pathway consists of a three-neuron chain.

• First-order neuron (central): Originates from the posterolateral hypothalamus, descends through the brainstem, and synapses at the ciliospinal center (Budge center) at C8–T2.
• Second-order neuron (preganglionic): Exits the spinal column, passes over the lung apex, ascends the cervical sympathetic chain, and synapses with the third-order neuron at the superior cervical ganglion.
• Third-order neuron (postganglionic): From the superior cervical ganglion, it forms a plexus around the internal carotid artery (ICA) and enters the cavernous sinus. In the posterior cavernous sinus, it leaves the ICA, briefly joins the abducens nerve (CN VI), then joins the first division of the trigeminal nerve (V1) and passes through the superior orbital fissure.

After passing through the posterior cavernous sinus, the sympathetic nerve innervates the dilator pupillae muscle via the nasociliary nerve → long ciliary nerves, and innervates Müller’s muscle and the inferior tarsal muscle via the sympathetic root of the ciliary ganglion → short ciliary nerves.

Course of the Abducens Nerve (Cranial Nerve VI)

The abducens nucleus is located in the caudal dorsal pons, just below the fourth ventricle. Nerve fibers exit the brainstem at the pontomedullary sulcus, enter the subarachnoid space, pass through Dorello’s canal, pierce the dura mater, and enter the cavernous sinus. Within the cavernous sinus, it runs just lateral to the internal carotid artery, passes through the superior orbital fissure into the orbit, and innervates the lateral rectus muscle. The abducens nerve runs adjacent to both the ICA and the ocular sympathetic nerve within the cavernous sinus.

Mechanism of Parkinson’s Sign

In the posterior cavernous sinus, the ocular sympathetic chain, after leaving the ICA, runs in close anatomical proximity to CN VI (briefly joining it). When a space-occupying lesion, vascular lesion, or inflammation occurs at this specific site, both are simultaneously damaged, resulting in Parkinson’s sign¹³.

This simultaneous impairment pattern is highly specific to the posterior cavernous sinus. In pontine lesions, even if the sympathetic nerve is damaged, it results in central (first-order neuron) Horner syndrome rather than postganglionic, so it does not meet the definition of Parkinson sign (postganglionic Horner syndrome + ipsilateral abducens nerve palsy). This localization specificity forms the basis of its clinical diagnostic value.

7. References

Footnotes

1. Ebner RN, Ribero Ayerza D, Aghetoni F. Sixth nerve palsy + ipsilateral Horner’s Syndrome = Parkinson’s Syndrome. Saudi J Ophthalmol. 2015;29(1):63-66. PMID: 25859142 / PMCID: PMC4314575 ↩ ↩² ↩³

2. Ngnitewe Massa R, Minutello K, Mesfin FB. Neuroanatomy, Cavernous Sinus. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. NBK ID: NBK459244 ↩

3. Kuybu O, Dossani RH. Cavernous Sinus Syndromes. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. NBK ID: NBK532976 ↩ ↩²

4. Erdal Y, Gunes T, Emre U. Isolated abducens nerve palsy: Comparison of microvascular and other causes. North Clin Istanb. 2022;9(4):353-357. PMID: 36276565 / PMCID: PMC9514074 ↩

5. Koc F, Kavuncu S, Kansu T, Acaroglu G, Firat E. The sensitivity and specificity of 0.5% apraclonidine in the diagnosis of oculosympathetic paresis. Br J Ophthalmol. 2005;89(11):1442-1444. PMID: 16234449 / PMCID: PMC1772929 ↩

6. Dutta P, Anand K. Tolosa–Hunt Syndrome: A Review of Diagnostic Criteria and Unresolved Issues. J Curr Ophthalmol. 2021;33(2):104-111. PMID: 34409218 / PMCID: PMC8365592 ↩