Irvine G. McQuarrie

Recovery from paraplegia caused by spontaneous spinal epidural hematoma

Three surgically treated cases of paraplegia caused by spontaneous spinal epidural hematoma are reported, along with summarized findings from 32 previously reported cases. Patients who recovered within 6 months had endured a shorter interval between loss of their ability to walk and surgical decompression than patients who did not recover (26 hours versus 48 hours; p < 0.02). When this interval exceeded approximately 36 hours, the probability of recovery fell below 50 percent.

Regeneration of adrenergic axons in rat sciatic nerve: Effect of a conditioning lesion

Abstract The rat sciatic nerve was crushed at the level of the mid-thigh (testing lesion), and the rate of outgrowth of the regenerating adrenergic axons was examined in the nerve. Two methods were used: (1) counts of axons containing norepinephrine demonstrable by histofluorescence; (2) measurement of the specific uptake of [3H] d,l -norepinephrine in vitro. In order to determine whether a prior nerve lesion had any effect on the outgrowth rate, all of the animals were subjected, two weeks prior to the testing lesion, to either a transection of the tibial branch of the sciatic nerve at the level of the ankle (conditioning lesion) or a sham operation. Counts of fluorescent axons made 3 days after the testing lesion showed that at 1.40 mm proximal to the lesion, the numbers of axons in both the conditioning-lesion group and the sham-operated group were not significantly different from non-lesioned animals. At a level 0.35 mm proximal to the testing lesion, counts in both groups were about 75% greater than at 1.40 mm, indicating that axonal sprouting had occurred. At 1.40 mm distal to the testing lesion, the numbers of axons had decreased by 9% in the sham-operated group, and by 24% in the group that had been subjected to a conditioning lesion (P The specific uptake of [3H] d,l -norepinephrine was measured 3 and 7 days after the testing lesion. The axonal component of uptake showed an approximately exponential decay with distance from the testing lesion; the leading edge of axonal uptake advanced at a rate of 3.9 ± 0.5 mm/day (S.E.) in the sham-operated group compared to 1.8 ± 0.6 mm/day (S.E.) in the conditioning-lesion group (P

Protein synthesis and fast axonal transport in regenerating goldfish retinal ganglion cells

To characterize the fast component of axonal transport in regenerating goldfish optic axons, the incorporation of L-2,3-[3H]proline into newly-synthesized proteins in the cell bodies of the retinal ganglion cells and the amount of transported labeled protein were determined at 2-36 days after cutting the optic tract. Both the incorporation and the amount of transported protein had doubled by 10 days after the lesion and continued to increase to about 5 times normal at 15 days, a time when a large proportion of the regenerating axon population had reached the optic tectum. Near-normal levels were recovered by 36 days. In contralateral control neurons, the incorporation of L-2,3-[3H]proline was unchanged from normal throughout, whereas the amount of labeled transported protein entering control axons was decreased by 55% at 2 and 10 days after the testing lesion, returning to normal by 15 days. An increase in fast transport velocity was seen in the regenerating axons beginning at 10 days after the lesion. However, a similar velocity increase was also seen in the contralateral control axons and in undamaged axons following removal of the cerebral hemispheres. Therefore, the velocity increase was not a specific consequence of axotomy.

Treatment of normal pressure hydrocephalus with low versus medium pressure cerebrospinal fluid shunts.

In a retrospective study, 39 patients received a low pressure (20 to 50 mm H2O) shunt and 33 received a medium pressure (55 to 85 mm H2O) shunt for the treatment of normal pressure hydrocephalus (NPH). Pre- and postoperative computed tomographic scans were obtained in 32 patients, permitting us to determine the influence of shunt pressure on ventricular size. A reduction in 3rd ventricle width was found to correlate with clinical improvement and was observed more frequently after the placement of a low pressure shunt than after the placement of a medium pressure shunt. When results were evaluated in patients who did not have advanced NPH or develop postoperative complications, gait was markedly improved in 60% of those receiving a low pressure shunt as opposed to 23% of those receiving a medium pressure shunt (P less than 0.05).

Effect of a Conditioning Lesion on Axonal Regeneration and Recovery of Function

Axonal regeneration following axotomy may be accelerated in neurons which have undergone a previous axonal injury. When axonal regeneration following an axotomy (the testing lesion) is altered as a result of the axon having undergone a previous injury (the conditioning lesion), we refer to this change as a conditioning lesion effect. The effect of a conditioning lesion is usually (but not always) an acceleration or enhancement of axonal outgrowth. It represents an interesting experimental manipulation which may shed light on the factors which initiate and control axonal regeneration. In this paper, we shall review current knowledge about conditioning lesion effects, present some new data, and discuss possible mechanisms and practical applications of conditioning lesion effects.

Effect of acetoxycycloheximide and dibutyryladenosine cyclic3′:5′-monophosphate on axonal regeneration in the goldfish optic nerve

Acetoxycycloheximide (AXM) or dibutyryl cyclic AMP (dbcAMP) was injected unilaterally into the vitreous humor of the eye beginning 5-6 days after bilateral optic nerve crush. Injections were repeated every 12-24 h for a total of 3-5 days; goldfish were sacrificed 10 days after lesioning the nerves. At a low dosage of AXM (0.1 microgram daily for 5 days), the mean outgrowth distance in treated neurons was 60% less than in contralateral control neurons. At a high dosage (0.3 microgram daily for 4 days), outgrowth was immediately blocked in both treated and contralateral control axons. Dibutyryl cyclic AMP, in a dose of 5 microM every 12 h for 3 days, produced a 38% reduction in outgrowth distance, associated with a 30% reduction in protein synthesis by the retinal ganglion cells and a 73% reduction in the amount of protein carried by the fast component of axonal transport.

Treatment of adult‐onset obstructive hydrocephalus with low‐or medium‐pressure CSF shunts

Nine patients with nontumor obstructive hydrocephalus of adult onset underwent 13 shunt placements; low-pressure valves (closing pressure, 20 to 50 mm H2O) were employed for 5 placements, and medium-pressure valves (closing pressure, 55 to 85 (mm H2O) were employed for 8 placements. The use of a low-pressure valve was followed by objective improvement in all five instances, whereas the use of a medium-pressure valve was followed by objective improvement in only two of eight instances (p = 0.021). The treatment of adult-onset obstructive hydrocephalus may require low-pressure shunts because of the high outflow resistance that characterizes this condition.

Principles of Neurosurgery

edited by Setti S. Rengachary and Robert H. Wilkins, ill., London, Wolfe, 1994. This single-volume work attempts to summarize the key points found in an encyclopedic multivolume text by the same editors (Neurosurgery, 2nd Ed., 1996). To achieve brevity, they have used over 200 color illustrations to convey the complexity of neurosurgical problems without need for a wordy text. Principles of Neurosurgery may meet many of the …

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