John P. Laurent

Topical Review: Birth-Related Upper Brachial Plexus Injuries in Infants: Operative and Nonoperative Approaches:

Advances in intraoperative neuroelectrodiagnostic testing and microneurosurgical techniques have made it possible to accurately explore the brachial plexus of neonates. Since 1987, we have followed 250 infants with birth-related brachial plexus injuries, and successful operations have been completed on more than 70 infants. Fifty infants who underwent surgery have been followed for more than 18 months. Based on these accumulated data and historical data, this review describes both nonoperative and operative approaches to the treatment of birth-related brachial plexus injuries. (J Child Neurol 1994;9:111-117).

A classification system for primitive neuroectodermal tumors (medulloblastoma) of the posterior fossa.

Tumors of the posterior fossa are described. Although the preoperative staging system of Chang and associates has proven prognostic relevance, a proposed new system may have even greater impact on prognosis because it considers the tumor burden postoperatively. This system (MAPS: metastasis, age, pathology, and surgery) incorporates age and pathologic characteristics into the staging system. The value of this proposed staging system, in particular, the impact of pathology, must be assessed in controlled trials. Cancer 56: 1807‐1809, 1985.

Spinal Metastasis in Primitive Neuroectodermal Tumors (Medulloblastoma) of the Posterior Fossa: Evaluation with CT Myelography and Correlation with Patient Age and Tumor Differentiation

Twelve consecutive children with primitive neuroectodermal tumors of the posterior fossa (PNET-PF) were evaluated for spinal metastases with CT metrizamide myelography (CTMM) in the early postoperative period. Metastases were identified in 5 children (42%) and all were noted to have deposits in the thoracic region. All children with metastases were less than 3 years old and had differentiated PNET-PF.

Tethered-cord syndrome after repair of meningomyelocele

The occurrence of tethered-cord syndrome is one of the delayed consequences of the repair of meningomyclocele. The existing neurological deficit worsens, or a new deficit is superimposed on the existing one. In addition, urological and orthopedic symptoms are also frequently encountered. Although radiological studies may be suggestive of tethering of the cord, not all children are symptomatic. Magnetic resonance imaging is the best radiologic study available. Ultrasonography, although economical and easy to perform, does not yield an optimal image. It appears that a careful periodic clinical evaluation is the best way to evaluate the patients for surgery.

Myelography for staging medulloblastoma

Thirty‐eight patients with newly diagnosed medulloblastoma were studied with myelography and cerebrospinal fluid (CSF) cytology studies before radiotherapy. Seventeen (45%) patients had evidence of dissemination beyond the posterior fossa. Spinal cord lesions were demonstrated in ten patients (26%). Negative results of CSF cytology studies did not preclude demonstration of cord involvement. Children younger than 5 years were more likely than older patients to have spinal cord involvement at diagnosis. Patients who were truly M‐0 did better in terms of absolute survival but not relapse‐free survival when compared with patients with dissemination. Myelography and cytology studies are necessary in the evaluation of all newly diagnosed patients with medulloblastoma and may also be indicated for patients with other brain tumors with a known propensity for dissemination. Cancer 56: 1763‐1766, 1985.

Effects of Ventricular Drainage and Dural Closure on Cerebrospinal Fluid Leaks after Posterior Fossa Tumor Surgery

In a retrospective study of 50 consecutive children with posterior fossa tumors treated at Texas Childrens Hospital, Houston, Tex., in 1989-1992, we evaluated perioperative factors which might influence the development of postoperative cerebrospinal fluid leaks. Factors analyzed included the presence of preoperative hydrocephalus, the institution of cerebrospinal fluid diversion, and the method of dural closure. No statistically significant impact on subsequent cerebrospinal fluid leakage was demonstrated.

Ventriculoatrial shunting via the azygos vein

The treatment of hydrocephalus has evolved through many stages but the “cure” is still elusive. It is not unusual for the neurosurgeon to find that the commonly used routes for catheter placement or sites for drainage of cerebrospinal fluid (CSF) cannot be employed. The azygos vein was used to gain access to the right atrium when the CSF could not be drained into the peritoneal cavity, nor could the neck veins be used to place the catheter into the right atrium. The azygos vein is a convenient and safe route to reach the right atrium in selected patients.

Primary leptomeningeal B‐cell lymphoma in an 8‐year‐old child

A case of primary leptomeningeal B‐cell lymphoma in an 8‐year‐old, previously healthy child is described. The child was found to have hypogammaglobulinemia, and the Epstein‐Barr virus genome was identified in cultured tumor cells despite blood serology being negative for the virus. The patient was treated with cyclophosphamide, doxorubicin, vincristine, and dexamethasone, plus intrathecal methotrexate, and initially improved. Before the initiation of craniospinal radiation, the patient developed progressive disease, deteriorated, and died 9 months after the onset of symptoms.

A new staging method versus TNM staging in children with posterior fossa primitive neuroectodermal tumor (medulloblastoma)

Prognostic factors were evaluated in 30 children with primitive neuroectodermal tumors of the posterior fossa (classical medulloblastoma or differentiated medulloblastoma). The preoperative TNM (Tumor, Node, Metastasis) staging system has been applied to estimate prognosis of patients with central nervous system tumors, but this system was not applicable in assessing the post-operative status of the tumor. To fill this need, a post-operative staging system was developed known as MAPS (Metastasis, Age, Pathology, Surgery), and in this report its efficacy is compared with that of the TNM system. The predictive values of MAPS staging in these 30 children were better than those obtained using the TNM method (MAPS r2=−0.90; TNM r2=−0.73; P<0.05).

Survival of split calvarial bone grafts in a dog model

To gain a better under-standing of the strength and long term viability of split calvarial bone graft, nine mongrel dogs each received four trephine craniotomies (1.5 mm diameter). The harvested bone plugs were split through the diploë and a partial-thickness plug was returned to each craniotomy site. The unused partial-thickness plugs underwent strength testing. After 90–150 days the dogs were sacrificed, bone scans and X-rays of the graft recipient sites performed, and the grafted plugs harvested for strength testing and histologic examination. Bone scanning showed increased osteoblastic activity within the grafts, strength testing showed a progressive loss in strength over the 150 days, and histologic examination demonstrated a creeping substitution. These results imply a similar evolution in strength and remodeling to that seen in long-bone grafts, whose remodeling typically spans 1 year.