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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.
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.
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
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Preoperative | ||||
Additional tests requested | MRI cine and CSF flow study |
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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 |
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Surgical microscope |
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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 |
Chiari malformation
Basilar invagination
Intracranial mass lesion causing displacement
Dandy-Walker malformation
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