Update: Overshunting associated myelopathy

Overshunting associated myelopathy” is a rare complication of CSF diversion that should be familiar to physicians who routinely evaluate patients with intracranial shunts 1) 2).

Only 12 previous cases have been reported in the literature 3).

OSAM has to be considered according to the Monro-Kellie hypothesis and is affected by an engorgement of the cervical epidural venous plexus, which can produce cervical myelopathy. Since it can be treated simply by increasing the shunt resistance, surgeons should be aware of the rarely detected overdrainage complication 4).

Classically, patients present with positional headache, but less common symptoms include neck pain and cranial nerve palsies.


A 45-year-old-patient with shunt-dependent, congenital hydrocephalus presented with an 8-year history of progressive tetraparesis and gait disorder in the Department of Neurosurgery, University of Tübingen, Germany. The patient was wheelchair-dependent. A new MRI scan of the head revealed slit ventricle syndrome and dural enhancement due to shunt overdrainage. An MRI and a CT-Phlebography of the cervical spine revealed engorgement of the epidural venous plexus with secondary compression of the spinal cord and myelomalacia. Surgery was performed during which we implanted a shunt valve. The patient recovered from surgery without any new deficits. The tetraparesis improved during the inpatient hospital stay. CT-Phlebography was performed 5 days after surgery and showed that the epidural venous plexus anterior to the cervical spinal cord had returned to nearly normal size. On follow-up examination 3 month after surgery, the patient´s strength had improved, and he was able to walk short distances with assistance and with ankle foot orthosis on the right side.

OSAM has to be considered according to the Monro-Kellie doctrine and is affected by an engorgement of the epidural cervical venous plexus, which can produce cervical myelopathy. Since it can be treated simply by increasing the shunt resistance, surgeons should be aware of the rarely detected overdrainage complication 5).


Ho et al., presented 2 cases of cervical myelopathy produced by engorged vertebral veins due to overshunting. Overshunting-associated myelopathy is a rare complication of CSF shunting. Coexisting cervical degenerative disc disease may further increase the difficulty of diagnosing the condition. Neurosurgeons and others who routinely evaluate patients with intracranial shunts should be familiar with this rare but possible diagnosis 6).


A 26-year-old woman with shunt-dependent, congenital hydrocephalus, presented with rapidly progressive cervical myelopathy following ventriculoperitoneal shunt revision. Imaging revealed engorgement of the cervical epidural venous plexus and mass effect on the cervical spinal cord. “Over-shunting associated myelopathy” is a rare complication of CSF diversion that should be familiar to physicians who routinely evaluate patients with intracranial shunts 7).

1) , 7)

Howard BM, Sribnick EA, Dhall SS. Over-shunting associated myelopathy. J Clin Neurosci. 2014 Dec;21(12):2242-4. doi: 10.1016/j.jocn.2014.05.014. Epub 2014 Jul 25. PubMed PMID: 25070631.

2) , 6)

Ho JM, Law HY, Yuen SC, Yam KY. Overshunting-associated myelopathy: report of 2 cases. Neurosurg Focus. 2016 Sep;41(3):E16. doi: 10.3171/2016.7.FOCUS16179. PubMed PMID: 27581312.

3) , 4) , 5)

Adib SD, Hauser TK, Engel DC, Tatagiba M, Skardelly M, Ramina K. Over-shunting associated myelopathy (OSAM) in a patient with bilateral jugular vein occlusion. World Neurosurg. 2018 Jun 1. pii: S1878-8750(18)31129-X. doi: 10.1016/j.wneu.2018.05.175. [Epub ahead of print] PubMed PMID: 29864573.

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