Horner Syndrome after chiropractic spinal manipulation

If you ask a chiropractor, you will probably be told that chiropractic spinal manipulation is a safe treatment. Unfortunately this is not quite true, as regular readers of this blog will appreciate. About half of all patients suffer mild to moderate adverse effects after chiropractic treatments and, in addition, many instances of much more serious complications have been documented, including rare cases of Horner syndrome. It results from an interruption of the sympathetic nerve supply to the eye and is characterized by the classic triad of miosis (ie, constricted pupil), partial ptosis, and loss of hemifacial sweating (ie, anhidrosis).

Danish neurologists recently reported the case of a 60-year-old man with no relevant medical history who was admitted to the Department of Neurology with drooping of his right upper eyelid and an ipsilateral contracted pupil, combined with pain, weakness, and numbness in his upper right limb.

The patient had experienced thoracic back pain of moderate intensity with radiating right-sided belt-like chest pain for 7 days. When the discomfort suddenly intensified, he sought chiropractic treatment. Following manipulations of the thoracic and cervical spine, the pain intensity initially lessened. Approximately one hour after chiropractic treatment, the patient experienced the eye and upper limb symptoms described above, for which he sought medical assistance three days later.

A detailed neurologic examination revealed moderate right-sided ptosis and miosis, no facial anhidrosis, decreased strength of the intrinsic and opponens muscles of the right hand, and reduced cutaneous sensation corresponding to the T1 dermatome, with inability to discriminate pain and light touch. The remaining clinical examination, routine blood tests, and vital parameters were unremarkable.

Brain CT scan and CT angiography including the aortic arch and neck vessels were performed and ruled out cerebral stroke and carotid artery dissection, respectively. As clinical signs of Horner syndrome and a concomitant radiating pain to the medial arm were considered suggestive of either a lower brachial plexopathy, i.e., due to a Pancoast tumor, or a radiculopathy, chest X-ray and electroneurography (ENG) were performed. No apical pulmonary pathology was detected. ENG of the right medial cutaneous antebrachial nerve demonstrated a normal sensory action potential (SAP), consistent with the lesion being located proximally to the dorsal spinal root ganglion, thus suggestive of a spinal nerve root lesion. A subsequent MRI of the thoracic spine showed a para-median herniation of the T1-T2 intervertebral disc compressing the right T1 spinal nerve root.

The patient received no surgery, and follow-up examination 6 months later revealed near-complete recovery, with only mild paraesthesia in the T1 segment of his right arm and a subtle ptosis remaining.

Horner syndrome due to a herniated thoracic disc has only been reported 6 times in the English language literature, though never preceded by chiropractic manipulation.

One of the most frequent causes of Horner syndrome is carotid artery dissection, which may occur spontaneously or due to local trauma to the neck region. Chiropractic manipulation as an independent risk factor for neck artery dissection and a consequent stroke is a controversial topic, though multiple cases of Horner syndrome due to ICA dissections subsequent to chiropractic manipulation have been reported. In the patient described here, an ICA dissection was considered unlikely due to the concomitant prominent radiating medial brachialgia and was furthermore ruled out by a CT angiogram of the neck vessels.

This patient experienced the onset of a Horner syndrome and ipsilateral upper limb symptoms shortly after chiropractic treatment, suggesting the cervico-thoracic manipulation as the cause of or at least worsening factor in the T1-T2 disc herniation. Several cases of disc herniations following chiropractic treatment have been reported.

While the definite pathophysiologic mechanism to explain this patient’s Horner syndrome remains unclear, it seems, according to the authors of this case-report, evident that manipulations as a minimum altered the configuration of an already existing disc protrusion.