Sweaty face: Unravelling the diagnostic dilemma of hemifacial hyperhidrosis

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A 38-year-old man presented to the dermatology outpatient with a 6-year history of excessive sweating on the left side of his face and absent sweating on the right side. He had no history of spinal trauma or autonomic dysfunction or family history of similar complaints. His physical and systemic examination revealed no abnormalities. Cutaneous examination revealed localised hyperhidrosis on the left side of the face, affecting areas corresponding to the V1, V2, V3, and C3 dermatomes [Figure 1a]. The starch-iodine test confirmed the absence of sweating on the right side of the face [Figure 1b]. Ophthalmological evaluation revealed miosis in the right eye and mild ptosis, while neurological examination demonstrated intact deep tendon reflexes without sensory deficits. His haematological and biochemical investigations, and screening for autoimmune diseases were unremarkable. Imaging in Horner syndrome aims to exclude serious lesions along the oculosympathetic pathway, such as brainstem stroke, demyelination, apical lung tumours, and carotid artery dissection. Magnetic resonance imaging (MRI) of the brain and magnetic resonance angiography (MRA) of the cerebral vessels were normal. However, dedicated imaging of the neck vessels using Computed Tomography Angiography (CTA) or MRA, which is crucial to rule out internal carotid artery dissection, could not be performed due to financial limitations. A CT scan identified a complete cervical rib on the right side, with anterior articulation at the first costochondral junction, and a partial cervical rib on the left [Figure 2]. Based on clinical findings and imaging, a diagnosis of Horner’s syndrome secondary to the cervical rib was made, and the patient was referred to neurosurgery for cervical rib excision. Cross-sectional imaging, such as CT or MR angiography of the thoracic outlet, is essential to assess neurovascular compression and guide surgical intervention. However, due to financial constraints, advanced imaging was not performed, and surgical excision could not be carried out.

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Figure 1a: Asymmetric sweating pattern showing localised hyperhidrosis over the left side of the face and anhidrosis over the right side.

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Figure 1b: Iodine starch test, after 10 minutes, the presence of sweating is indicated by the onset of a dark-blue colour on the left side of the face, and the absence of sweating on the right side of the face is indicated by no colour change.

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Figure 2: Computed tomography of the thorax revealing a complete cervical rib on the right side with anterior articulation at the first costochondral junction (red arrow), and a partial cervical rib on the left (yellow arrow).

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Sweating is an essential thermoregulatory mechanism regulated by the sympathetic nervous system. Disruption in this system can lead to disorders like hyperhidrosis, which significantly impacts quality of life. Hyperhidrosis can be localised or generalised, with axillae, soles, palms, and face commonly affected sites.¹ Primary hyperhidrosis is mostly idiopathic, but secondary causes may include rare neurological disorders. Horner’s syndrome, first described by François Claude Bernard in 1854, is a rare secondary cause of hyperhidrosis. It manifests with a triad of ptosis, miosis, and anhidrosis due to disruption of the sympathetic nerve supply.² Common causes of Horner’s syndrome include tumours, trauma, and vascular lesions. Cervical ribs are congenital anomalies seen in approximately 0.2% to 1.0% of the general population and are usually detected incidentally on chest radiographs.³ Horner syndrome results from disruption of the oculosympathetic pathway, which comprises a three-neuron arc. The first-order neuron originates in the posterior hypothalamus, descends through the brainstem, and synapses at the ciliospinal centre of Budge (C8-T2). The second-order (preganglionic) neuron exits the spinal cord, ascends over the lung apex and subclavian artery, and synapses in the superior cervical ganglion. The third-order (postganglionic) neuron then travels with the internal carotid artery into the cavernous sinus and reaches the eye and facial sweat glands via the ophthalmic division (V1) of the trigeminal nerve. In our patient, the lesion is consistent with second-order neuron involvement, due to thoracic outlet compression from a cervical rib. In Horner’s syndrome, the anhidrosis seen on one side of the face contrasts with hyperhidrosis on the unaffected side. Pharmacologic confirmation of Horner syndrome typically uses topical cocaine (2-10%) eye drops, which block norepinephrine reuptake. The presence of persistent anisocoria (≥0.8 mm) post-instillation confirms the diagnosis.⁴ Apraclonidine (0.5-1%), now widely available, is considered a more sensitive and preferred first-line agent. However, pharmacologic testing is warranted only when the diagnosis is uncertain. In this case, the presence of the full clinical triad and an identifiable anatomic cause rendered additional testing unnecessary. Cervical ribs are rare congenital anomalies that can compress surrounding neurovascular structures, potentially disrupting the sympathetic pathway. While cervical ribs are associated with thoracic outlet syndrome, their role in causing Horner’s syndrome and hyperhidrosis is less commonly reported. Imaging is essential for evaluating these patients, especially when accompanied by localised symptoms. Non-urgent imaging is recommended for patients without trauma or other localising signs.⁵ Multidisciplinary management, involving dermatology, neurology, and surgery is crucial for optimal outcomes. This case highlights a rare presentation of hemifacial hyperhidrosis in Horner’s syndrome secondary to a cervical rib.