Teaching Case

A 54-year-old gentleman with a long-standing history of low-back pain presented to the Orthopaedic out-patient clinic with worsening symptoms and new left leg pain within the distribution of the L5 nerve root. Nerve root compression was suspected and an MRI scan arranged.

Sequences: Sagittal T1 and T2-weighted images were performed through the lumbar spine. Axial T1 and T2-weighted images were performed through the lower four lumbar intervertebral discs (© Ablett M, Department of Radiology, Ayr Hospital, Ayr, Scotland).

An additional axial T2-weighted image has also been included (© Poe LB (2008) Ventriculus Terminalis. MRI Web Clinic).

Findings: Sagittal T2-weighted images revealed a slit-like area of high signal, identical to CSF, with the terminal spinal cord just proximal to the conus medullaris.

The axial T2-weighted image obtained at T12-L1 level confirms the typical intra-medullary location of CSF signal intensity.

These findings are noted in conjunction with a slightly low-lying conus.

Bulging of the L2/3 intervertebral disc without significant cord impingement and a reduction in signal intensity in the L2/3, L3/4 and L5/S1 intervertebral discs were also demonstrated.

Ventriculus terminalis, first described by Stilling (1859) [1], is an anatomical variant of the spinal cord. Krause (1875) [2] introduced the term ‘fifth ventricle’ to describe this anomaly of the distal cord which he characterised as an ependymal lined, cystic structure originating within the conus medullaris. Kernohan (1924) [3] later described the development of the ventriculus terminalis, explaining that it arises during the secondary neuralation phase of embryonic life. A caudal cell mass of undifferentiated cells undergoes vacuolisation and canalisation, merging with the rostral spinal cord. Subsequent retrogressive differentiation results in involution of the distal cord and formation of the ventriculus terminalis. The variable nature of this apoptotic process thus accounts for the differing appearances of the ventriculus terminalis. Accordingly, it is a phenomenon more frequently encountered in infancy with Coleman (1995) [4] identifying ventriculus terminalis in 11 of 418 children (2.6%), each of whom was less than 5 years old.

Patients presenting with unexplained, recurrent low back pain/sciatica in whom a conservative management approach has failed may merit investigation with MR imaging [5]. Ventriculus terminalis, rarely encountered in the adult population, often reflects an incidental finding rather than an explanation for a patient's symptoms. However, in a small proportion of patients the ventriuclus terminalis may dilate, resulting in a spectrum of symptoms allowing patients to be classified into three groups, Cystic Lesion of the Ventriculus Terminalis types I-111 [6]:

CLVT Type I: Non-specific neurological symptoms.
CLVT Type II: Focal neurological deficit.
CLVT Type III: Bowel or bladder dysfunction.

In this case the patient's symptoms may in part be attributable to minor tethering of the cord. The association with ventriculus terminalis has been demonstrated, mainly in the paediatric population [7].

The ventriculus terminalis appears as a well-defined, small, ovoid, fluid-filled cavity of CSF signal within the conus medullaris [8]. It is non-enhancing following contrast administration thus allowing it to be differentiated from a cystic neoplasm or cord infarction. Although knowledge of typical location may allow discrimination of ventriculus terminalis from a syrinx, should such a lesion develop within the distal cord then serial imaging may be required to achieve an accurate diagnosis.

If discovered incidentally, no intervention is necessary and treatment focuses on any other underlying pathology. Literature suggests that patients with CLVT Type I are also best managed conservatively whilst those within the CLVT Types II and III benefit from surgical intervention [6].

Ventriculus terminalis is a rare finding in adulthood and without dilatation, is generally of no clinical significance.