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Dean Chou, Prakash Sampath and Henry Brem

Hemorrhagic vestibular schwannomas are rare entities, with only a few case reports in the literature during the last 25 years. The authors review the literature on vestibular schwannoma hemorrhage and the presenting symptoms of this entity, which include headache, nausea, vomiting, sudden cranial nerve dysfunction, and ataxia. A very unusual case is presented of a 36-year-old man, who unlike most of the patients reported in the literature, had clinically silent vestibular schwannoma hemorrhage. The authors also discuss the management issues involved in more than 1000 vestibular schwannomas treated at their institution during a 25-year period.

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Dean Chou, Phillip B. Storm and James N. Campbell

Object. Autologous bone graft harvesting from the iliac crest remains the gold standard for fusion surgery. One disadvantage of autologous bone harvesting is the patient's enduring postoperative pain at the donor site. Nerve injury is one of the postulated mechanisms that may account for this pain. The object of this study was to determine whether the lateral cutaneous branch of the subcostal nerve is vulnerable to injury in the process of obtaining grafts from the anterior iliac crest.

Methods. Anatomical dissections were performed on 10 cadaveric specimens to ascertain the size of the T-12 subcostal nerve and its position in relation to the iliac crest.

Conclusions. The lateral cutaneous branch of the subcostal nerve may lie as close as 6 cm from the anterior superior iliac spine. This nerve is very vulnerable to injury when harvesting bone from the anterior iliac crest. Knowledge of the anatomy may decrease the risk of injury to this nerve.

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Frank L. Acosta Jr., Cynthia T. Chin, Alfredo Quiñones-Hinojosa, Christopher P. Ames, Philip R. Weinstein and Dean Chou

Establishing the diagnosis of cervical osteomyelitis in a timely fashion is critical to prevent catastrophic neurological injury. In the modern imaging era, magnetic resonance imaging in particular has facilitated the diagnosis of cervical osteomyelitis, even before the onset of neurological signs or symptoms. Nevertheless, despite advancements in diagnosis, disagreement remains regarding appropriate surgical treatment. The role of instrumentation and type of graft material after cervical decompression remain controversial. The authors describe the epidemiological features, pathogenesis, and diagnostic evaluation, and the surgical and nonsurgical interventions that can be used to treat osteomyelitis of the cervical spine. They also review the current debate about the role of instrumentation in preventing spinal deformity after surgical decompression for cervical osteomyelitis. Based on this review, the authors conclude that nonsurgical therapy is appropriate if neurological signs or symptoms, instability, deformity, or spinal cord compression are absent. Surgical decompression, debridement, stabilization, and deformity correction are the goals once the decision to perform surgery has been made. The roles of autogenous graft, instrumentation, and allograft have not been clearly delineated with Class I data, but the authors believe that spinal stability and decompression override creating an environment that can be completely sterilized by antibiotic drugs.

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Pregnancy-related vertebral hemangioma

Case report, review of the literature, and management algorithm

John H. Chi, Geoffrey T. Manley and Dean Chou

Pregnancy is a recognized risk factor for quiescent vertebral hemangiomas becoming symptomatic; this usually occurs during the 3rd month of gestation. The natural history of these lesions is poorly understood, and treatment practices must consider the overall safety of the mother and fetus. The authors report a case of cervical vertebral hemangioma presenting during the 24th week of pregnancy and review the current literature.

A 26-year-old woman in her 24th week of pregnancy presented with upper-back pain and progressive spastic paresis in the legs. Neuroimaging studies revealed a diffuse C-7 vertebral body lesion with extradural extension and compression of the spinal cord consistent with a vertebral hemangioma. Successful decompression was accomplished, and the fetus experienced no adverse effects from the surgery.

In a review of the literature, 23 cases of pregnancy-related vertebral hemangioma dating back to 1927 were identified. Prepartum surgical decompression was performed in eight patients, postpartum surgery was performed in 12, and surgery was not performed in four. Overall, patients experienced excellent neurological recovery, regardless of the severity and duration of spastic paresis.

Observation should be considered for symptomatic patients at greater than 32 weeks gestation. Surgery should be considered for patients with severe neurological deficits at less than 32 weeks of gestation.

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Dean Chou, Adolfo Espinoza Larios, Robert H. Chamberlain, Mary S. Fifield, Roger Hartl, Curtis A. Dickman, Volker K. H. Sonntag and Neil R. Crawford

Object

A flexibility experiment using human cadaveric thoracic spine specimens was performed to determine biomechanical differences among thoracolumbar two-screw plate, single-screw plate, and dual-rod systems. A secondary goal was to investigate differences in the ability of the systems to stabilize the spine after a one- or two-level corpectomy.

Methods

The authors evaluated 21 cadaveric spines implanted with a titanium mesh cage and three types of anterior thoracolumbar supplementary instrumentation after one-level thoracic corpectomies. Pure moments were applied quasistatically while three-dimensional motion was measured optoelectronically. The lax zone, stiff zone, and range of motion (ROM) were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Corpectomies were expanded to two levels, and testing was repeated with longer hardware.

Biomechanical testing showed that the single-bolt plate system was no different from the dual-rod system with two screws in limiting ROM. The single-bolt plate system performed slightly better than the two-screw plate system. Across the same two levels, there was an average of 19% more motion after a two-level corpectomy than after a one-level corpectomy. In general, however, the difference across the different loading modes was insignificant.

Conclusions

Biomechanically, the single-screw plate system is equivalent to a two-screw dual-rod and a two-screw plate system. All three systems performed similarly in stabilizing the spine after one- or two-level corpectomies.

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Dean Chou, Roger Hartl and Volker K. H. Sonntag

✓ Conus medullaris injury from burst fractures is known to occur in conjunction with other neurological deficits, including lower-extremity motor weakness or sensory changes. Rarely does an isolated conus medullaris injury occur from an extradural cause without other neurological deficits. The authors report four cases of L-1 burst fractures in which conus medullaris dysfunction was the sole neurological injury in the absence of lower-extremity involvement.

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Roger Härtl, Robert H. Chamberlain, Mary S. Fifield, Dean Chou, Volker K. H. Sonntag and Neil R. Crawford

Object

Two new techniques for atlantoaxial fixation have been recently described. In one technique, C-2 intra-laminar screws are connected with C-1 lateral mass screws; in the second, C-1 and C-3 lateral mass screws are interconnected and C-2 is wired sublaminarly. Both techniques include a C1–2 interspinous graft. The authors compared these techniques with the gold-standard, interspinous graft–augmented C1–2 transarticular screw fixation and with a control C1–2 interspinous graft fixation procedure alone.

Methods

In six human cadaveric occiput–C4 specimens, nonconstraining 1.5-Nm pure moments were applied to induce flexion, extension, lateral bending, and axial rotation during which three-dimensional angular motion was measured optoelectronically. Each specimen was tested in the normal state, with graft alone (after odontoidectomy), and then in varying order after applying each construct with a rewired graft. All three constructs allowed significantly less angular motion at the C1–2 junction than the wired interspinous graft alone during lateral bending and axial rotation (p < 0.01, paired Student t-test) but not during flexion or extension. Transarticular screw fixation with an interspinous graft allowed less motion at the atlantoaxial junction than the two new constructs in several conditions. Differences were greater between the transarticular screw construct and the intralaminar screw construct than between the transarticular screw construct and the C1–3 lateral mass screw construct. During lateral bending and axial rotation, the C1–3 construct allowed less motion at the atlantoaxial junction than the intralaminar screw construct.

Conclusions

Biomechanically, the gold-standard C1–2 transarticular screw fixation outperformed the two new techniques during lateral bending and axial rotation. Wiring C-2 to C1–3 rods provided greater stability than C1–2 laminar screws, but it sacrificed C2–3 mobility. It is unknown whether the small differences observed biomechanically would lead to clinically relevant differences in fusion rates.

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Dean Chou, Justin S. Smith and Cynthia T. Chin

✓The authors describe a case of a discal cyst that resolved almost completely without direct intervention. Discal cysts are rare, with the authors of only a few case reports describing this entity. These reports all identify at least some intervention performed for alleviation of the symptoms, including open surgery, minimally invasive surgery, or percutaneous puncture with aspiration. The authors report on a 35-year-old man with radiculopathy who presented with a discal cyst and was treated with a routine epidural injection and selective nerve root block. Within 5 months, the discal cyst showed dramatic regression on magnetic resonance imaging and the patient’s symptoms improved. The natural history of this pathological entity is unknown, and to the authors’ knowledge this is the first detailed report of the regression of a discal cyst without surgery or aspiration.

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Laurence A. G. Marshman

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Dean Chou, Daniel C. Lu, Philip Weinstein and Christopher P. Ames

✓Expandable cages are frequently used to reconstruct the anterior spinal column after a corpectomy. The forces that are used to expand these cages can be large, depending upon the mechanism of expansion. To the authors' knowledge, there have been no reports of adjacent-level vertebral body fracture after placement of expandable cages. The authors report 4 cases of adjacent-level vertebral body fractures after placement of expandable cages. This study found that the fracture pattern in the coronal plane was similar in all cases.