Conjoined cranial nerves diagnosed with high resolution steady state free precession MRI: First case

Conjoined cranial nerves diagnosed with high resolution steady state free precession MRI: First case

Summary: Conjoined nerve root is a type of developmental anomaly involving nerve root. It is common in spinal nerve roots, commonly seen in lumbar region and never reported in cranial nerve roots. The incidence of conjoined lumbar nerve root (CLNR) up to 14% has been reported in cadaveric studies 1 and up to 6% in recent prospective MRI study 2. Since first described in 1949, more than 120 cases of CLNR have been reported 2. We also found a few reports of conjoined cervical nerve root 3, however conjoined cranial nerve root (CCrNR) has never been reported in world literature till date. We report the first case of CCrNR diagnosed with magnetic resonance (MR) imaging using high resolution steady state free precession (SSFP) sequence. In this, bilateral trigeminal (CN5), facial (CN7) and vestibulocochlear (CN8) nerves emerge as a conjoined nerve root from lower lateral pons, then courses in cisternal segments and subsequently divides into individual nerves to enter into the internal acoustic meatus (IAM) and Meckel’s cave. CCrNR were diagnosed using MR imaging using high resolution SSFP, because of its ability to generate a strong signal in tissues that have a high T2/T1 ratio such as cerebro-spinal fluid (CSF). Thus, it is particularly useful in visualizing the cisternal segments of the cranial nerves as they provide excellent contrast resolution between CSF and nerves, as well as high spatial resolution4. Association of CLNR with vertebral anomalies has been described in literature5. Congenital block vertebrae at C2-C3 and C4-C5 levels were also noted in our case of CCrNR. Case history: Clinical presentation: A 32 yr male presented with neck pain and hedache. There was no radiation of pain to the upper limbs. There was no history of tingling or numbness in upper limbs. Central nervous system and systemic examination were normal. Laboratory tests were normal. Imaging findings and diagnosis: First standard MRI brain with spin echo sequences was performed, which was normal. Then high resolution MR imaging with the SSFP sequence of the skull base region was conducted in 60 contiguous 1-mm-thick slices in the plane of the optic chiasm and major cranial nerves. Axial SSFP at the level of lower pons showed bilateral sensory roots of CN5 emerging from lower lateral pons along with CN7 and CN8 nerves as a common trunk. Further, these common trunks were seen coursing through the cerebellopontine angle (CPA) cisterns and subsequently divided into individual nerves just before IAM to enter into the Meckel’s cave and IAM (Fig 1). Coronal reformation of SSFP showed both common trunks including the sensory root of CN5 lying infero-lateral to and far away from motor nerve roots of CN5 which exits at its normal mid pons level (Fig 2). Motor root normally runs inferolateral with the sensory root (Fig 3), whereas in this case reversal of relation of sensory and motor nerve roots of CN5 was noted. Continuous scrolling of SSFP axial sequence from above

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  • DR.SHARAD MALVADKAR 2016-01-25 17:56:53

    Conjoined cranial nerve have never been reported in word literature till date. This is first case of conjoined cranial nerve. please go through and invite the case for publication in JRCR