The influence of tumor topography on the surgical outcome of craniopharyngiomas

OBJECTIVE

Various topographical classifications for craniopharyngioma have been proposed based on their relationship with optic chiasm and the third ventricular floor. There is a paucity of literature evaluating the surgical outcome based on tumor topography. This study aims to compare the surgical outcomes of retrochiasmatic craniopharyngiomas (RCPs) and nonretrochiasmatic craniopharyngiomas (non-RCPs).

METHODS

This retrospective study includes newly diagnosed patients with craniopharyngioma who underwent surgery between January 2000 and December 2015. Clinical features, the extent of resection (EOR), surgical outcomes, tumor recurrence, and progression-free survival (PFS) of craniopharyngiomas were compared with respect to their relationship to the optic chiasm and third ventricular floor.

RESULTS

The authors identified RCPs in 104 and non-RCPs in 33 patients. RCPs were significantly larger and more associated with hydrocephalus than were non-RCPs (p < 0.001) at the time of diagnosis. Puget grade 2 hypothalamic involvement was more frequent with RCPs. EOR and PFS following either subtotal resection (p = 0.07) or gross-total resection (p = 0.7) were comparable between RCPs and non-RCPs. There was no significant difference in the postoperative visual outcome. Resection of RCPs resulted in higher postoperative hypopituitarism (64% vs 42%, p = 0.01) and hypothalamic dysfunction (18% vs 3%, p = 0.02). Location of the tumor, either retrochiasmatic (HR 0.5; 95% CI 0.14-2.2; p = 0.4) or nonretrochiasmatic (HR 1.3; 95% CI 0.3-5.5; p = 0.6), did not show association with recurrence. RCPs with extra- and intraventricular components (type 3b) had a higher incidence of postoperative hypothalamic morbidities (p = 0.01) and tumor recurrence (36% vs 19%; p = 0.05) during follow-up than the extraventricular (type 3a) RCP. Between prechiasmatic and infrachiasmatic/intrasellar craniopharyngiomas, EOR (p = 0.7), postoperative diabetes insipidus (p = 0.4), endocrinological outcome (p = 0.7), and recurrence (p = 0.1) were comparable. The patients with complex multicompartmental tumors had a lower rate of gross-total resection (25%, p = 0.02) and a higher incidence of tumor recurrence (75%, p = 0.004) than the rest.

CONCLUSIONS

The tumor topography can influence the postoperative outcome. RCPs can be associated with a higher incidence of hypopituitarism and hypothalamic morbidities postoperatively. The influence of topography on EOR and tumor recurrence is controversial. However, this study did not find a significant difference in EOR and tumor recurrence between RCPs and non-RCPs. PFS and overall mortality are also comparable.

Total external ophthalmoplegia and orbital apex syndrome as first presenting feature of Rhabdomyosarcoma involving petrous part of the temporal bone: A case report

INTRODUCTION AND IMPORTANCE

Rhabdomyosarcoma (RMS) can have various unusual presentations. We report an unusual presentation of RMS as orbital apex syndrome in a six-year-old boy involving the petrous part of the temporal bone.

CASE PRESENTATION

A six-year-old boy presented with drooping of the left eyelid for seven days associated with headache, left-sided hearing loss, and nasal blockage. Contrast-enhanced magnetic resonance imaging (CE-MRI) brain and orbit revealed an ill-defined expansile vascular lesion centered at the petrous part of the left temporal bone with extension to the cavernous sinus, which was confirmed as RMS on histopathology and immunohistochemistry. The patient was managed by chemotherapy and radiotherapy.

CLINICAL DISCUSSION

RMS is the most common aggressive malignant soft tissue tumor in the pediatric population. It accounts for 4-8 % of all malignancies in children below 15 years of age, with strong male preponderance. The most common site for RMS is head and neck (45 %), having maximum incidence during the first decade of life.

CONCLUSION

Total external ophthalmoplegia in a child is an acute emergency; it should be properly worked up, and neuroimaging should always be advised. Prompt diagnosis and management by a multidisciplinary team can be both life and sight-saving.

Tubercular Subdural Empyema with Tubercular Abscess: Lessons Learnt

Tuberculosis (TB) is still one of the major health care problems in many developing countries. Among various forms of TB, central nervous system (CNS) TB causes significant morbidity and mortality. CNS TB can present in various forms: cerebritis, abscess, meningitis, tuberculoma, calcified granuloma, meningitis, or hydrocephalus. But subdural empyema is a very rare form of presentation. Very few cases have been reported till now in the literature. So, high level of suspicion, thorough microbiological and histological investigations to diagnosis, and early and timely inception of anti-TB medication are keys in its management. Here, we are presenting a case of tubercular subdural empyema that was successfully treated with surgical evacuation and anti-TB medication.

Impact of the COVID-19 Pandemic and Lockdown on Non-COVID Neurosurgical Patients: Lessons Learned

Objective The COVID-19 pandemic has challenged the basic functioning of the health care system. There has been an adverse impact on non-COVID-19 patients due to a shift in healthcare delivery, which is underreported. This study aims to explore the impact of the pandemic on various aspects of non-COVID neurosurgical patients.

Methods This descriptive cross-sectional study was conducted with a structured questionnaire to assess the physical, economic, and psychological impacts of the COVID-19 pandemic and lockdown measures on neurosurgical patients presenting to our hospital after a nationwide lockdown.

Results Among 203 patients, non-neurotrauma and neurotrauma cases were 175 (86%) and 28 (16%), respectively. Among non-neurotrauma patients, 130 (64%) patients had cranial pathology. All 56 (27.6%) preoperative patients experienced rescheduling of surgery. Among 52 postsurgical patients, 47 (90%) had their adjuvant therapy delayed. Forty patients experienced deterioration in their neurological symptoms. Seventy-six (37%) patients sought medical attention from private hospitals. A severe contraction of income (≥ 25% of the income before lockdown) was experienced by families of 29 (14.3%) patients. Severe and very severe stress have been experienced by 24 (11.8%) and 14 (6.9%) patients, respectively. Severe and very severe anxiety was experienced by 32 (15.8%) and 9 (4.4%) patients.

Conclusion The COVID-19 pandemic and nationwide lockdown had a tremendous impact on the physical, social, and psychological well-being of patients with non-COVID illnesses. We are yet to face the long-term implications of the delay due to this pandemic in scheduled surgical and adjuvant treatments of non-COVID neurosurgical patients.

Use of Marker Computed Tomography as a Navigational Tool for Performing Minicraniotomies

We want to highlight a simple technique for performing smaller craniotomies, using a marker computed tomography scan, which does not require any special equipment, training or cost and is not time-consuming. Pictorial description of two such cases have been provided.

Clinical Profile and Treatment Outcome of Spinal Epidural Arachnoid Cysts: A Systematic Review of Case Studies and Reports

Background A spinal epidural arachnoid cyst (SEAC) is a rare clinical entity. We performed a systematic review of the literature to obtain information regarding demographics, clinical presentation, treatment modalities, and outcome of SEACs.

Methods A literature search was performed by using the databases PubMed/Medline, PubMed Central, Embase, Cochrane Library, Ovid MEDLINE, and Ovid Medline In-Process. A total of 170 articles were found on literature search. We found 575 cases of SEAC since 1904 for inclusion in the review including three cases which were operated by us. We studied the patient characteristics, clinical features, and management strategies, and evaluated their outcome.

Results The average age of presentation was 30 years with a male:female ratio of 1.03:1. They are commonly seen in the thoracic region (42.3%). The length of cyst was more than two vertebral levels in 85.81%. Mean symptom duration was 29 months, with most common presentation being that of compressive myelopathy. A good clinical outcome was present in symptomatic patients who had a shorter symptom duration and underwent complete surgical excision of the SEAC. Age, sex, length of lesion, and presence of dural defect did not have a bearing on the surgical outcome.

Conclusion For thoracic compressive myelopathy in a young patient, SEAC should be kept as a differential diagnosis. Surgical complete excision of the cyst with meticulous closure of the dural defect is the standard in management for a good clinical outcome.

Migrating Souvenir Bullet: The Management Dilemma

The cranio-cerebral trauma following gunshot injuries has high mortality and morbidity, with 66% to 90% victims dying before reaching hospital and only half of those treated in hospital surviving. However, in case of most salvageable patients, the question which poses dilemma to treating physicians is the decision as to when and why remove the retained missile.

A 21-year-old man was observing a gunfight in the street from his balcony. Suddenly something struck his forehead and there was a small amount of bleeding toward the medial end of his left eyebrow. He had moderate headache and dizziness. Because of nonresolution of headache over seven days he was hospitalized and underwent X ray of the skull and CT of the head, which showed a retained metallic bullet in left inferior parieto-occipital region without any significant hemorrhage. As there was no neurological deficit or meningeal signs, he was managed conservatively. His symptoms improved gradually within next week and he was discharged home. His most recent follow-up was 28 months since injury and imaging showed migration of the bullet to the right inferior temporal region. As he was completely asymptomatic throughout, no intervention was offered. However, long-term follow-up for potential complications of migration, hydrocephalus, and abscess formation is advisable.

Partial occlusion of left axillary artery in a patient undergoing robot-assisted radical cystectomy

Robot-assisted surgeries are associated with steep positions which provide free operative field to surgeons; however, it becomes more challenging to the anaesthesiologists. In robot-assisted surgery, the patient is not usually accessible after docking in of robot, so monitors, circuits and tubes should be tightly secured and confirmed before handing over the patient to the surgeons. We report a patient with partial left axillary artery occlusion in a patient posted for robot-assisted radical cystectomy.

A Systematic Review on the Impact of the COVID-19 Pandemic on Neurosurgical Practice and Indian Perspective

OBJECTIVE

The study objective was to systematically review the impact of the current pandemic on neurosurgical practice and to find out a safe way of practicing neurosurgery amid the highly infectious patients with COVID-19.

MATERIALS AND METHODS

A review of the PubMed and EMBASE databases was performed. The literature was systematically searched using keywords such as "COVID-19" and "Neurosurgery."

RESULTS

Among the 425 records, 128 articles were found to be eligible for analysis. These articles described the perspectives of the neurosurgical departments during the pandemic, departmental models, and organizational schemes for triaging emergent and nonemergent neurosurgical cases for the optimal utilization of limited resources, and solutions to continue academic and research activities. Triaging systems help us to optimally utilize the limited resources available. Guidelines have been developed for safe neurosurgical practice and for the continuation of clinical and academic activities during this pandemic by various national and international neurosurgical societies. Key changes in the telemedicine regulatory guidelines would help us to continue to provide neurosurgical care. Videoconferences, online education programs, and webinars could help us to overcome the disadvantages brought upon the neurosurgical education by the social-distancing norms.

CONCLUSION

In an unprecedented time like this, no single algorithm is going to clear the ethical dilemma faced by us. Individual patient triage is a way for maintaining our ethical practice and at the same time, for efficiently utilizing the limited resources. As the pandemic progresses, new guidelines and protocols will continue to evolve for better neurosurgical practice.

"Locked up inside home" - Head injury patterns during coronavirus disease of 2019 pandemic

BACKGROUND

As citizens have been forced to stay home during coronavirus disease of 2019 (COVID-19) pandemic, the crisis created unique trends in the neurotrauma patterns with changes in mode, severity, and outcome of head injured patients.

METHODS

Details of neurotrauma admissions under the neurosurgery department at our institute since the onset of COVID-19 pandemic in the country were collected retrospectively and compared to the same period last year in terms of demographic profile, mode of injury, GCS at admission, severity of head injury, radiological diagnosis, management (surgical/conservative), and outcome. The patients were studied according to which phase of pandemic they were admitted in - "lockdown" period (March 25 to May 31, 2020) or "unlock" period (June 1 to September 15, 2020).

RESULTS

The number of head injuries decreased by 16.8% during the COVID-19 pandemic. Furthermore, during the lockdown period, the number of admissions was 2.7/week while it was 6.8/week during the "unlock" period. RTA was the mode of injury in 29.6% patients during the lockdown, while during the unlock period, it was 56.9% (P = 0.000). Mild and moderate head injuries decreased by 41% and severe head injuries increased by 156.25% during the COVID-19 pandemic (P = 0.000). The mortality among neurotrauma patients increased from 12.4% to 22.5% during the COVID-19 era (P = 0.009).

CONCLUSION

We observed a decline in the number of head injury admissions during the pandemic, especially during the lockdown. At the same time, there was increase in the severity of head injuries and associated injuries, resulting in significantly higher mortality in our patients during the ongoing COVID-19 pandemic.

Primary anaplastic lymphoma kinase-negative anaplastic large cell lymphoma of cervical spine presenting with quadriplegia: A case report and literature review

Background:

An anaplastic large cell lymphoma (ALCL) involving the cervical spine and leading to quadriplegia is very rare.

Case Description:

A 48-year-old immunocompetent male presented with quadriplegia that warranted an anterior cervical corpectomy/fusion. He was previously being presumptively treated for cervical disease attributed to tuberculosis. The histopathology and immunohistochemistry revealed an ALCL that was anaplastic lymphoma kinase (ALK) negative. The patient had a favorable response to surgery followed by CHOEP (cyclophosphamide, doxorubicin, vincristine, etoposide, and prednisolone) chemotherapy.

Conclusion:

ALK-negative ALCL presenting with quadriplegia due to primary involvement of cervical spine is extremely rare, but must be diagnosed and appropriately managed.

Dysembryoplastic Neuroepithelial Tumor: A Rare Brain Tumor with Excellent Seizure Control after Surgical Resection

Introduction Dysembryoplastic neuroepithelial tumor (DNET) is a rare cause of intractable epilepsy, which has excellent results in terms of seizure control after surgical resection. We present one such case, because of its rarity, to highlight the effect of tumor removal on seizure control, particularly DNET.

Materials and Methods/Case Summary A 9-year-old male patient presented with sudden onset of partial seizures for the past 6 months. There were five episodes. In each episode, the patient engaged in irrelevant talk, followed by deviation of mouth to left and twitching movements. The episode lasted 5 minutes and there was no loss of consciousness. There was no aura or tongue bite, and in one of the episodes, the patient lost consciousness. There was no other significant positive history. On examination, the child was consciously alert, without focal neurological deficit or features of meningitis. There was no papilledema. The patient was on phenytoin sodium, phenobarbitone and clobazam. Magnetic resonance imaging (MRI) of brain was done with and without contrast. MRI revealed a lesion approximately 4.1 × 3.6 × 3.2 cm in the right medial temporal lobe. It was hypointense to brain on T1 and fluid-attenuated inversion recovery (FLAIR), and hyperintense on T2-weighted images. Diffusion restriction was present and there was minimal contrast uptake. There was no evidence of mass effect or midline shift After discussing the risks and benefits with parents, the patient underwent preanesthetic checkup, and was taken up for craniotomy and excision of tumor. Gross total excision was done. The child was started orally on day 1 postoperatively and ambulated. There were no further seizure episodes. The patient was continued on phenytoin and clobazam, and phenobarbitone was tapered gradually. At 6 months, the child was seizure-free.

Conclusions DNET are rare tumors occurring early in life and presenting with intractable seizures. Surgical resection offers a good and safe chance for long-term seizure control.

Surgery for Spinal Trauma: Early Days at a Young Institution in a Hilly State

Background Spinal trauma is associated with significant morbidity and affects the overall quality of life of the patient as well as their family. The aim of this study was to study the epidemiology, in-hospital outcome, and follow-up of patients undergoing surgery for spinal trauma.

Methods All patients who underwent surgery for spinal trauma at the Department of Neurosurgery between June 2016 and October 2019 were studied retrospectively. Data collected from patient record included demographic profile, mode of injury, level of injury, neurological status at admission, time from injury to operative intervention, hospital stay, neurological outcome at discharge, and follow-up. Postoperative computed tomography scans were done in all patients to check for adequacy of screw placement.

Results A total of 70 patients (45 males, 25 females) with a mean age of 36 years (range: 16–65 years) were operated for spinal injuries at our department during the study period. Fall was the most common mode of injury (77.1%), followed by road traffic accident (28.5%). Most common site of injury was lumbar spine (38.6%), followed by dorsal (32.9%) and cervical (28.5%). Out of the total, 27.1% of our patients were American Spinal Injury Association (ASIA) grade A at presentation whereas 18.6% were ASIA E. Remaining 54.3% patients had incomplete injuries (ASIA B, C, and D). Burst fracture was the most common morphology of injury (60%), followed by translational injuries (30%). Mean duration between injury and operative intervention was 20.8 days. The mean duration of hospital stay was 21.4 days (range: 8–90 days). Six patients expired during hospitalization. All these six cases had cervical spinal injury. One patient of dorsal spine injury with a complete neurological injury expired 6 months after discharge from the hospital (cause unknown). Nine of our cases showed neurological improvement on follow-up and in rest of the patients, neurological status remained same as preoperative status.

Conclusion Neurological status at admission (ASIA grade) and level of injury remain the most important predictor of the outcome. Spinal injury patients must be managed with a holistic and multidisciplinary approach. Rehabilitation is important for helping these patients in leading a productive life.

Rare Case of Sellar and Suprasellar Metastasis from Ewing's Sarcoma of Tibia

We hereby report a case of metastatic Ewing's sarcoma presenting with rapid-onset total ophthalmoplegia, optic atrophy, and right temporal hemianopia. Comprehensive ophthalmic and neurological evaluation with targeted radioimaging revealed a tumor mass centered over the sella, compressing optic chiasma, extending to involve the left cavernous sinus and the left orbital apex. Whole-body imaging revealed the evidence of multifocal lung and mediastinal metastasis with focal lytic defect in the left femoral head. Histopathological evaluation of transnasal punch biopsy from the nasopharyngeal extension of the tumor revealed small round-cell tumor with strong CD99 positivity, supporting the diagnosis of Ewing's sarcoma. Rapid, aggressive extensions of the metastatic tumor into vital structures despite the initiation of chemoradiation of the extensive intracranial tumor led to unexpected demise of the patient. Our case is an unusual case of Ewing's sarcoma metastasis manifesting as a sellar mass and mimicking a pituitary adenoma radiologically, with a rapid progression within 2 weeks to cause massive extension of tumor into suprasellar, infrasellar, and left parasellar area, indicative of highly malignant nature of the tumor.

Giant Occipitocervical Encephalocele

Encephaloceles are cranial defects in which sac contains herniating brain, which is often gliotic. Congenitally, this defect may extend into posterior elements of cervical vertebrae and leads to occipitocervical encephalocele. When the size of this sac is larger than head size, they are termed as giant. Very young age and associated congenital anomalies in these patients pose significant challenges in diagnostic, anesthetic, and surgical techniques. We share a case of giant occipitocervical encephalocele managed at our institute and discuss about its management issues with review of literature.

Spinal tumors: Trends from Northern India

Introduction and Methods:

We retrospectively analyzed 111 patients with spinal tumors operated over a period of 9 years to observe the relative frequency of different lesions, their clinical profile, functional outcome and prognostic factors. 30/111 (27%) were extradural, 40/111 (36.1%) were intradural extramedullary (IDEM) and 41/111 (36.9%) were intramedullary spinal cord tumors (IMSCTs). Mean age at surgery was 30.81 years (range 1–73 years). The average preoperative duration of symptoms was 16.17 months (15 days to 15 years). Major diagnoses were ependymomas and astrocytomas in IMSCT group, schwanommas and neurofibromas in IDEM group, and metastasis, lymphoma in extradural group. The common clinical features were motor weakness in 78/111 (70.27%), sensory loss in 55/111 (49.54%), pain 46/111 (41.44%), and sphincter involvement in 47/111 (42.43%) cases.

Results:

Totally, 88/111 (79.27%) patients had improvement in their functional status, 17/111 (15.31%) remained same, and 6/111 (5.4%) were worse at time of their last follow-up. The mean follow-up was 15.64 months (1.5 m⁻¹⁰ years). Totally, 59 out of 79 patients, who were dependent initially, were ambulatory with or without the aid. Most common complication was persistent pain in 10/111 (9%) patients and nonimprovement of bladder/bowel symptoms in 7/111 (6.3%). One patient died 3 months after surgery.

Conclusions:

(1) Congenital malformative tumors like epidermoids/dermoids (unrelated to spina bifida) occur more frequently, whereas the incidence of spinal meningioma is less in developing countries than western populations. (2) The incidence of intramedullary tumors approaches to that of IDEM tumors. Intramedullary tumors present at a younger age in developing countries. (3) Rare histological variants like primitive neuroectodermal tumors should also be considered for histological differential diagnosis of spinal tumors. (4) Preoperative neurologic status is the most important factor related to outcome in spinal tumors.

Sporotrichosis in Amritsar--a case report

A case of cutaneous, lymphatic Sporotrichosis, in a farm labourer, is presented. The diagnosis was established by isolating fungus from the lesion. Dimorphic nature of the fungus was established in vitro by demonstrating the mycelial phase at 25-30 degrees C and yeast phase at 37 degrees C. The patient responded well to oral administration of Potassium iodide.

An in vivo evaluation of the ENDEX and RCM Mark II electronic apex locators in root canals with different contents

The accuracy of many apex locators is affected by electrolytes including sodium hypochlorite. According to the manufacturer a new device, the ENDEX, overcomes this problem. The purpose of this study was to assess the accuracy of the ENDEX in comparison with a traditional device, the RCM Mark II. The lengths of 61 canals with various contents (vital pulp, necrotic pulp, pus/exudate, sodium hypochlorite, and water) were determined in vivo. Files were cemented within the canals at lengths determined by the ENDEX. The teeth were then radiographed and extracted, and the distance between the file tip and apical foramen was recorded. Derived readings for the RCM Mark II were compared with the actual ENDEX reading and corresponding radiograph. The results indicated that most of the file tips that were at the radiographic apex actually extended through the apical foramen, and canal content had a varying effect on each device. The overall accuracy of the ENDEX (71.7%) was higher than that of the RCM Mark II (43.5%) within 0.5 mm of the apical foramen. The ENDEX, unlike the RCM Mark II, proved accurate in the presence of sodium hypochlorite.

Respiratory distress in newborn: treated with ventilation in a level II nursery

Fifty consecutive neonates with respiratory distress persisting beyond 6 h of age were studied during a 18 month period (total deliveries 2000/y). Twenty two neonates were managed with oxygen hood with increasing oxygen concentration, 28 with continuous positive airway pressure (CPAP) ventilation using a nasal cannula. Of these babies on CPAP, 10 were shifted to intermittent positive pressure ventilation (IPPV) on a pressure limited, time cycled ventilator (Neovent, Vickers). Babies were monitored with continuous hemoglobin oxygen saturation (SaO2), hourly blood pressure and vital charting. Radial arterial blood gas analysis (ABG) was done when feasible and especially on clinical deterioration. Oxygen (FiO2 0.95) from an oxygen concentrator was used as a source of continuous supply of oxygen. Commonest cause of respiratory distress was hyaline membrane disease (18%), followed by wet lung syndromes (14%), meconium aspiration (12%), asphyxia (12%) and septicemia (8%). In 8 babies, a lung biopsy (postmortem) was done to confirm the diagnosis. Nineteen of the 50 babies with respiratory distress died, there was a survival of 50% on CPAP and 30% on IPPV. No case of oxygen toxicity or other major complications was encountered. Even with moderate resources, neonatal ventilation in a Level II nursery is a challenging task. Babies less than 1000g require aggressive measures which is not very economical in a special care baby unit (SCBU).

Multidrug resistant typhoid fever: study of an outbreak in Calcutta

Of 103 cases of typhoid fever admitted to the Pediatric Wing of our hospital during the months of August 1989 to April 1990, 82.5% were resistant to chloramphenicol, ampicillin and co-trimoxozole. Nearly 87% children were in the age group of 3-10 years. Fever was present in all and splenomegaly in 90.2% cases. Urinary retention during the course of illness was present in 2 cases. The positivity rate of blood culture, bone marrow culture and Widal test was 83.7, 100 and 13.5%, respectively. Majority of the strains were of Phage 51-Type I. For the treatment of multidrug resistant cases gentamicin and furazolidine proved ineffective. Ciprofloxacin was tried in 85 cases and was found to be effective in all cases with no side effects.

Depletion of reserve in the hemopoietic system: I. Self-replication by stromal cells related to chronologic age

Transplanted devascularized mouse femurs and spleens or spleens ligated in situ all undergo a period of massive necrosis followed by a period of cellular regeneration and reconstitution of tissue components. This renewal of stromal tissue is endogenous to the organ and proliferates inward from a thin rim of surviving cells. Components of the femoral or splenic stroma constitute a hemopoietic microenvironment whose functions include the lodgment, commitment to differentiation and support of the proliferation of hemopoietic stem cells and their differentiating descendents. By using measures of the ability to support hemopoiesis, and the histological appearance of the reconstituted hemopoietic organs, it was shown that the degree of regeneration of the stroma was inversely related to its chronological age. Thus, although age-related changes in stromal cells are not readily demonstrable in hemopoietic tissue during a normal lifespan, they are in process and can be made obvious under anoxic conditions causing cell death followed by an unusual demand for cell replication. Key cellular components of such aged tissues apparently have either lessened resistance to anoxia or a reduction in replicative potential or both. The second alternative interpretation suggests an analogy in vivo to mesenchymal-cell clonal attenuation observed in vitro.