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Chiari malformation with recurrent symptoms


Introduction

As described in Chapter 67 , Chiari I malformation is a condition derived from the abnormal caudal displacement of the cerebellar tonsils through the foramen magnum into the upper cervical canal, often with intramedullary cyst formation. Surgical treatment is advocated for symptomatic patients and for those harboring syringomyelia. Currently, suboccipital bony decompression with duraplasty is the treatment of choice for restoration of adequate cerebrospinal fluid (CSF) flow and symptom relief. However, persistent or recurrent syringomyelia after foramen magnum decompression is not uncommon, with rates ranging from 22% to 66%. Despite adequate posterior fossa decompression and initial clinical improvement, persistent or enlarging syringomyelia and tonsillar herniation can occur. Therefore, routine clinical and radiological follow-up is mandatory. There is some data indicating that the timing of the initial operation plays a role in influencing the need of reoperation, especially in patients undergoing primary surgery before age 5. This complication is less likely when decompression is accompanied by duraplasty. Contrary to the initial management of Chiari I malformations, the rationale for operative treatment is not clear in cases of failed surgery and no standard treatment has been established. Despite this, persistent or enlarging symptomatic syringomyelia is an important indication for surgical intervention. Redo posterior fossa decompression should address the reimpactation of the foramen magnum and the aberrant CSF flow through it. When a large syringomyelia is present, a syringo-pleural or syringo-subarachnoid shunt should be considered. In this chapter, we describe the case of a young female patient with recurrent tussive headaches 1 year after posterior fossa decompression and duraplasty.

Example case

  • Chief complaint: headaches, upper extremity paresthesias

  • History of present illness: This is a 42-year-old female patient with a history of previous Chiari I malformation treated with suboccipital craniotomy and C1 laminectomy/duraplasty 1 year prior. Initially her symptoms of tussive headaches improved, but in the last month, the headaches have returned. In addition, she has developed paresthesias in both upper extremities and mild gait disturbances. The patient underwent radiological evaluation that showed a large spinal cord fluid-filled cavity compatible with syringomyelia ( Fig. 68.1 ). In addition, an obstruction at the level of the fourth ventricle was elucidated on cine magnetic resonance imaging.

    Fig. 68.1, Preoperative imaging of the craniocervical junction. (A) T1-weighted axial and sagittal magnetic resonance imaging (MRI) demonstrating absence of cerebellar tonsil caudal displacement. (B) Sagittal computed tomography scan (bone window) demonstrated previous suboccipital craniectomy and the absence of the C1 posterior arch. No obvious Chiari malformation was identified. (C) Sagittal T2 MRI demonstrating a large fluid-filled cavity compatible with the presence of a syrinx affecting from C3 to T1. The dilation of the cord is more significant at the C6-T1 levels.

  • Medications: antidepressants

  • Allergies: no known drug allergies

  • Past medical and surgical history: as above

  • Family history: none

  • Social history: none

  • Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; interossei 5/5; iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 5/5

  • Reflexes: 3+ in bilateral biceps/triceps/brachioradialis with positive Hoffman; 3+ in bilateral patella/ankle; no bilateral feet clonus, and positive Babinski; sensation decreased in both upper (C6 and C7 distribution); mild gait instability

  • Hazem Eltahawy, MD

  • Neurosurgery

  • St. Mary Mercy Hospital

  • Ain Shams University

  • Livonia, Michigan, United States

  • George I. Jallo, MD

  • Neurosurgery

  • Johns Hopkins All Children’s

  • Tampa, Florida, United States

  • Sheng-Fu Lo, MD

  • Neurosurgery

  • Johns Hopkins

  • Baltimore, Maryland, United States

  • Khoi D. Than, MD

  • Neurosurgery

  • Duke University

  • Durham, North Carolina, United States

Preoperative
Additional tests requested MRI cine and CSF flow study

  • MRI C-spine flexion-extension

  • MRI brain and complete spine

  • EMG

  • MRI brain and complete spine with cine CSF flow study

  • C-spine flexion-extension x-rays

  • MRI C-spine flexion-extension

  • Low volume lumbar puncture with CSF analysis

  • Neurology evaluation

MRI brain with CSF flow study
Surgical approach selected Revision suboccipital decompression and possible C6–7 laminectomy for syringo-pleural shut Revision suboccipital decompression and possible C5–6 laminectomy for syringosubarachnoid shunt Revision suboccipital craniectomy, C1 laminectomy with possible tonsillar coagulation with obex stenting Conservative management pending flow studies
Goal of surgery Restoration of CSF flow Recreate CSF flow and treat syrinx Reestablish CSF flow Possible syringo-subarachnoid shunt if symptoms worsen
Perioperative
Positioning Prone, with pins Prone, with pins Prone on Jackson table, with pins
Surgical equipment

  • Surgical microscope

  • Ultrasound

Surgical microscope

  • Surgical microscope

  • Ultrasound

Medications MAP >80 Steroids Steroids
Anatomical considerations Vertebral arteries, PICA, medulla, cerebellum Foramen magnum, floor of fourth ventricle PICA branches, choroid plexus
Complications feared with approach chosen CSF leak, vascular or neural injuries CSF leak, hydrocephalus, neurological deficits PICA injury, choroid plexus bleeding, hydrocephalus
Intraoperative
Anesthesia General General General
Exposure Occiput-C1 Occiput-C1 Occiput-C1
Levels decompressed Occiput-C1 Occiput-C1 Occiput-C1
Levels fused None None None
Surgical narrative Position prone on gel rolls and Mayfield pins, midline craniocervical incision along prior incision, careful dissection down to bony edges or prior craniectomy and C1, widen bony decompression at foramen magnum and C1, excision of thickened scar on top of dural graft, assessment of flow with ultrasound, V or Y-shaped durotomy under microscope, lysis of any arachnoid bands around cerebellar tonsils and brainstem, possible shrinking of tonsils with bipolar if needed, duroplasty with dural substitute, water tight closure confirmed with Valsalva, supplement with dural sealant, reassess CSF flow with ultrasound, layered closure with antibiotic irrigation, be prepared for syringo-pleural shunt if intraoperative findings dictate, flat for 12–24 hours Position prone with neck flexion, open old incision, identify normal anatomy, open dura, utilize microscope to inspect obex and outflow of fourth ventricle, one- to two-level cervical laminectomy if no adhesions seen, open dura, visualize spinal cord and perm midline myelotomy in the thinnest area, place syringo-subarachnoid shunt, secure stent with 8-0 Prolene, watertight dural closure Position prone with neck flexion, subperiosteal dissection down to suboccipital bone and prior craniotomy flap, blunt dissection over cut edge of posterior arch of C1, remove prior craniotomy, intraoperative ultrasound to confirm exposure and absence of normal CSF pulsations, Y-shaped dural opening across prior graft, avoid injury to PICA while dissecting and cutting arachnoid adhesions, mobilize cerebellar tonsils to access obex and floor of fourth ventricle, possibly coagulate tonsils if needed to access obex, open up membrane to confirm CSF pulsatile flow from the fourth ventricle through the median aperture, avoid manipulation of the roof, consider stenting with shunt tubing with extra holes and anchored with pial stitch, watertight expansile duraplasty with a reverse triangle pattern, fibrin sealant, replace craniotomy flap, layered closure
Complication avoidance Widen bony decompression at foramen magnum and C1, assessment of flow with ultrasound, possible shrinking of tonsils with bipolar if needed, syringo-pleural shunt if intraop findings dictate Find normal anatomy, evaluate flow of fourth ventricle, syringo-subarachnoid shunt if no adhesions in fourth ventricle, secure shunt down Ultrasound to evaluate CSF pulsations, observe for PICA when dissecting, possible tonsillar coagulation, possible stenting to keep aperture open
Postoperative
Admission ICU ICU ICU
Postoperative complications feared CSF leak, vascular or neurological injury, persistent syrinx CSF leak, hydrocephalus, neurological deficits Chemical meningitis, pseudomeningocele, unrecognized bleeding causing hydrocephalus, PICA injury
Anticipated length of stay 1–2 days 4–5 days 2–3 days
Follow-up testing MRI C-spine prior to discharge, 3 months after surgery MRI brain and cervical spine 3 months after surgery MRI C-spine with CINE 4–6 weeks after surgery CSF flow study in 6 months
Bracing None None None
Follow-up visits 2 weeks, 6 weeks, 3 months after surgery 10–14 days after surgery 2 weeks after surgery
CSF , Cerebrospinal fluid; EMG , electromyography; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MEP , motor evoked potential; MIS , minimally invasive surgery; MRI , magnetic resonance imaging; PICA , posterior inferior cerebellar artery; SSEP , somatosensory evoked potential.

Differential diagnosis

  • ▪

    Chiari malformation

  • ▪

    Basilar invagination

  • ▪

    Intracranial mass lesion causing displacement

  • ▪

    Dandy-Walker malformation

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