Symptom recurrence after suboccipital decompression for pediatric Chiari I malformation: analysis of 256 consecutive cases.

McGirt MJ, Attenello FJ, Atiba A, Garces-Ambrossi G, Datoo G, Weingart JD, Carson B, Jallo GI. Symptom recurrence after suboccipital decompression for pediatric Chiari I malformation: analysis of 256 consecutive cases. Childs Nerv Syst. 2008 Nov;24(11):1333-9.

OBJECTIVE:
Symptom recurrence remains a problem for some patients after surgical decompression for Chiari I malformation. We set out to identify variables at presentation that could identify subgroups most likely to experience incomplete symptom relief after hindbrain decompression for Chiari I malformation.

MATERIALS AND METHODS:
We retrospectively reviewed the records of all pediatric patients undergoing first-time suboccipital decompression for Chiari I malformation over a 10-year period. Measured outcomes included (1) persistence or recurrence of symptoms regardless of severity and (2) need for revision decompression.

RESULTS:
Two hundred fifty-six children (10 5 years old) underwent surgery for Chiari I malformation and were followed up for a mean of 27 months. Presenting symptoms included headache in 192 (75%) patients and brainstem or cranial nerve symptoms in 68 (27%) patients. Fifty-seven (22%) patients experienced mild to moderate symptom recurrence. Nineteen (7%) patients required revision decompression for significant symptom recurrence. Headache was 70% more likely to persist or recur versus cranial nerve or brainstem symptoms (relative risk 1.70, p < 0.05). Vertigo and frontal headache independently increased the odds of symptom recurrence 2.9- and 1.5-fold, respectively. Each increasing year of preoperative headache duration was independently associated with 15% increase in likelihood of symptom persistence (p < 0.05). Severe tonsilar ectopia (caudal to C2 lamina) was twice as likely to require revision decompression (14% versus 6%). CONCLUSION: In our experience, recurrence of mild symptomatology not severe enough to justify revision surgery may occur in nearly a fifth of patients after surgery. Headache was more likely to recur than objective cranial nerve or brainstem symptoms. Increasing duration of headaches, frontal headaches, and vertigo may be more refractory symptoms of Chiari I malformation. PMID: 18516609

Brainstem dysfunction in chiari malformation presenting as profound hypoglycemia: presentation of four cases, review of the literature, and conjecture as to mechanism.

Rekate HL, Nadkarni TD, Teaford PA, Wallace D.
Brainstem dysfunction in chiari malformation presenting as profound hypoglycemia: presentation of four cases, review of the literature, and conjecture as to mechanism. Neurosurgery. 1999 Aug;45(2):386-91. Review.

OBJECTIVE:
We report four patients whose cases resulted in our observation that profound hypoglycemia resulting from intermittent hyperinsulinism plays a significant role in patients with brainstem dysfunction from Chiari I or II malformations who have intermittent autonomic dysfunction ("blue spells").

METHODS:
The records of four children with severe brainstem dysfunction associated with hindbrain herniation (Chiari I or II malformation) were reviewed retrospectively. Each patient had severe lower cranial nerve dysfunction that required tracheotomy and feeding tube placement. After we found that profound hypoglycemia had occurred during a spell of autonomic dysfunction in one patient, the charts of the other three patients were reviewed for evidence of hypoglycemia. Now, whenever one of them has evidence of autonomic dysfunction, prospective studies of glucose and insulin levels are performed. Three of the patients had Chiari II malformation in association with myelomeningocele, and one patient had a Chiari I malformation resulting from Pfeiffer's syndrome.

RESULTS:
Hypoglycemia occurred in these patients episodically, and usually when their shunts were functioning. The hypoglycemia was associated with hyperinsulinemia in each patient. The brainstem structures of these children (presumably the dorsal motor nuclei of the vagus) were extremely sensitive to changes in local or regional intracranial pressure. These changes were triggered by intermittent shunt failure, agitation from pain, abdominal distention from constipation, and retention of CO2. In patients with Chiari malformations, even mild increases in intracranial pressure lead to brainstem dysfunction. One possible explanation is that pressure on the deformed Xth cranial nerve nuclei may lead to insulin release and life-threatening hypoglycemia. Continuous-drip feeds are necessary to prevent this complication.

CONCLUSION:
Patients with severe intermittent brainstem dysfunction after decompression of Chiari I or Chiari II malformations should have laboratory studies of glucose levels performed at the time of the episodes to rule out hypoglycemia.


PMID: 10449086

Assessment of brainstem function in Chiari II malformation utilizing brainstem auditory evoked potentials (BAEP), blink reflex and masseter reflex.

Koehler J, Schwarz M, Boor R, Hölker C, Hopf HC, Voth D, Urban PP, Ermert A. Assessment of brainstem function in Chiari II malformation utilizing brainstem auditory evoked potentials (BAEP), blink reflex and masseter reflex. Brain Development. 2000 Oct;22(7):417-20.

Brainstem dysfunction was evaluated in 67 patients with myelomeningocele and Chiari II malformation using brainstem auditory evoked potentials (BAEP), blink reflex (BR) and masseter reflex (MR). Signs and symptoms related to Chiari II malformation were observed in 18 patients while 49 patients had normal brainstem findings. BAEP and BR showed a higher sensitivity of brainstem involvement than MR (BAEP=1.0, BR=0.83, MR=0.50). BR, and in particular, MR were of higher accuracy (BR=0.52, MR=0.72) than BAEP (0.39) in separating patients with brainstem signs and symptoms related to Chiari II malformation. We feel that this is due to anatomic and physiologic peculiarities of the brainstem structures mediating BR and MR. Our results suggest that brainstem reflexes can support the decision of further treatment.

PMID: 11102725

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Electrophysiological studies on brainstem function in patients with myelomeningocele

Mori K, Nishimura T. Electrophysiological studies on brainstem function in patients with myelomeningocele. Pediatric Neurosurgery. 1995;22(3):120-31.

We investigated the brainstem auditory evoked potentials (BAEPs), somatosensory evoked potentials (SEPs), and electrically elicited blink reflexes (BRs) to evaluate the brainstem function in 31 patients with meyelomeningocele (MMC) including 22 with Chiari type-II malformation. The I-III interpeak latency (IPL) of the BAEPs and the N9-N13 IPL of the SEPs tended to become gradually prolonged from the normal range with increasing age. The III-V IPL of the BAEPs and the N13-N20 IPL of the SEPs were initially prolonged and decreased progressively to the normal range. These findings indicated a gradual latency shortening of the brainstem components and latency prolongation of the peripheral components. Thus, while primary brainstem dysfunction may improve with age, secondary dysfunction due to stretching and elongation of the lower cranial nerves and cervical nerve roots may intensify. The BRs showed an abnormal R2 in 90% of the cases, disclosing subclinical lesions in the medulla oblongata which were not detected by BAEPs alone. BAEPs, SEPs and BRs were combined to yield a functional evaluation of the brainstem and lower cranial nerves that could not be done by magnetic resonance imaging alone. No close relation was found between electrophysiological abnormalities and the degree of hindbrain anomaly by neuroimaging.

PMID: 7786804

Somatosensory evoked potentials to median nerve stimulation in meningomyelocele

Nishimura T, Mori K. Somatosensory evoked potentials to median nerve stimulation in meningomyelocele: what is occurring in the hindbrain and its connections during growth? Childs Nervous System. 1996 Jan;12(1):13-26. Review.

Twenty patients with meningomyelocele (MMC) and shunted hydrocephalus, ranging in age from 3 to 23 years old, underwent serial recording of short-latency somatosensory evoked potentials (SEPs) to median nerve stimulation, on the basis of which to assess the evolution of dysfunction in the brainstem and its connections (cervical spinal cord, cervical nerve roots, lower cranial nerves). Eighteen patients had Chiari type II malformations, none of which was symptomatic. In all 20 patients, serial SEP recordings were obtained repeatedly after periods ranging from 2 to 7 years. The results were as follows: (1) the ratio of EP-N13 interpeak latencies (IPLs) to body height (BH) tended to lengthen gradually after starting in the normal range with growth. (2) In contrast, the ratio N13-N20 IPLs/BH decreased continuously to the normal range with growth, after initial prolongation. These findings and our earlier studies of brainstem auditory evoked potentials suggest that compression and traction result in strangulation of the cervical spinal cord and kinked medulla as well as stretching of the cervical nerve roots and lower cranial nerves. However, primary intrinsic functional disorders of the brainstem appeared to improve gradually during growth. The natural history of Chiari type II malformations involves these opposing dynamic phenomena in the hindbrain and its connections.

PMID: 8869170