Hydrocephalus Case File

Hydrocephalus Case File

Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 54

A 9-year-old boy is brought to the pediatrician because of severe headaches over the past week. The headaches were initially present only in the morning but over the last 48 h have become constant, lasting all day long. The child has also been vomiting and complains of problems “seeing.” On examination, his temperature is 98°F and his heart rate is 80 beats/min. The child appears to be lethargic and is sensitive to the lights in the room. He has some neck rigidity, and his gait seems to be unsteady. Otherwise the examination is normal. A CT scan of the head is performed urgently and reveals bilateral enlargement of the frontal horns of the lateral ventricles and the third ventricle.

⯈ What is the most likely diagnosis?

⯈ Where is the obstruction most likely located?

ANSWER TO CASE 54:

Hydrocephalus

Summary: This is a 9-year-old child with progressive headache over 1 week, vomiting, and visual disturbances. On examination, the child has lethargy, photosensitivity, neck rigidity, and an unsteady gait. CT imaging shows lateral and third ventricle enlargement.

• Most likely diagnosis: Hydrocephalus

• Obstruction: Most likely the aqueduct of Sylvius leading to bilateral lateral ventricle and third ventricle enlargement.

CLINICAL CORRELATION

Hydrocephalus is the accumulation of cerebrospinal fluid in the brain. This increased CSF can be due to increased production, disturbance in flow, or altered absorption. Symptoms depend on the age of the patient and the rapidity of development. In this case, the child has an acute onset (less than 1 week) leading to more dramatic symptoms. If the hydrocephalus developed slowly such as over months, the only symptoms may be a vague headache and memory problems. With acute hydrocephalus, the most common complaint is headache. Children often are lethargic or have insomnia; if these symptoms are significant, they can also lead to vomiting. This child also has mild sensitivity to light (photophobia) and neck stiffness (rigidity), which are indications of meningeal irritation. Acute meningitis or blood in the CSF can also cause these symptoms. A brain tumor is another possibility; imaging of the brain is important to rule out the condition. In this case, significant hydrocephalus is identified on the CT scan. Because the lateral ventricles and the third ventricle are dilated, the most likely location of the obstruction is at the aqueduct of Sylvius. The treatment is to relieve the CSF accumulation, which usually involves a shunt placement procedure; a ventriculoperitoneal route is most commonly used. Surgical relief of the obstruction may also be attempted.

APPROACH TO:

Ventricular System of the Brain

OBJECTIVES

1. Be able to describe the location of the ventricles and circulation of CSF

2. Be able to identify the choroid plexus in the lateral, third and fourth ventricles, and the arachnoid granulations in the superior sagittal sinus.

DEFINITIONS

CHOROID PLEXUS: A structure in the ventricles of the brain where cerebrospinal fluid (CSF) is produced. The choroid plexus consists of modified ependymal cells.

ARACHNOID GRANULATIONS: Protrusions of arachnoid mater through the dura mater into the venous sinuses of the brain, allowing CSF to exit the subarachnoid space and return to the venous system. Most of the arachnoid granulations can be found in the superior sagittal sinuses.

DISCUSSION

There are four ventricles in the brain. The lateral ventricles are located within the cerebral hemispheres. The third ventricle is located between the diencephalons, and the fourth ventricle is located between the brainstem and the cerebellum (see Figure 54-1).

The paired lateral ventricles are the largest in the ventricle system of the brain and are each composed of one body and three horns: the anterior or frontal horn extends into the frontal lobe, the posterior or occipital horn extends into the occipital lobe, and the lateral or temporal horn extends into the temporal lobe. The body of the lateral ventricle is the central portion and is found in the parietal lobe just posterior to the frontal horn. The inner surface of the lateral ventricles is covered by a thin epithelial membrane called the ependyma. In the central portion and temporal horns of the ventricle, the ependyma is folded into the cavity with capillaries to form the choroid plexus, which produces CSF. CSF produced in the lateral ventricles flows into the third ventricle through interventricular foramen of Monro.

The third ventricle is a narrow, slitlike space. The choroid plexus is found in the superior part of this ventricle close to the interventricular foramen. The cerebral aqueduct of Sylvius conducts CSF from the third ventricle to the fourth ventricle.

The fourth ventricle has a tentlike configuration. The rhomboid fossa of the brainstem forms the floor, and the superior and inferior medullary velum of the cerebellum form the roof of this ventricle. The choroid plexus is found in the inferior part of this ventricle. From the fourth ventricle, CSF flows into the subarachnoid space through the foramina of Magendie and Luschka.

After the CSF circulates into the subarachnoid space and surrounds the brain and spinal cord, it is drained into the venous sinuses via the arachnoid granulations located mostly in the superior sagittal sinus (see Figure 54-2).

Increasing production of CSF, decreasing the absorption of CSF, or blocking the flow of CSF will cause it to accumulate in the ventricles, leading to hydrocephalus.

Figure 54-1. (a) Three-dimensional lateral view of the ventricles of the brain; (b) location and circulation of the cerebrospinal fluid (CSF). (Reproduced, with permission, from Morton DA, Foreman KB, Albertine KH. The Big Picture: Gross Anatomy. New York: McGraw-Hill Medical, 2011. Figure 16-2.)

Figure 54-2. Flowchart showing circulation of CSF in the subarachnoid space.

COMPREHENSION QUESTIONS

54.1 A 32-year-old woman is seen in the emergency department complaining of severe headaches and difficulty walking. She is noted to be lethargic. On CT imaging of the head, she is noted to have enlargement of bilateral lateral ventricles and the third ventricle. The fourth ventricle is noted to be normal. The most likely obstruction in this patient is the

    A. Foramen of Luschka

    B. Foramen of Magendie

    C. Cerebral aqueduct

    D. Interventricular foramen of Monro

    E. Cisterna magna

54.2 Lumbar puncture may be performed to withdraw CSF for lab examination. During this procedure, which the following structures will the needle pass through before it enters the subarachnoid space?

    A. Supraspinous ligament

    B. Anterior longitudinal ligament

    C. Posterior longitudinal ligament

    D. Intertransverse ligament

    E. Pia mater

54.3 During the lumbar spinal puncture, the needle usually should be inserted in the midline between the spinal processes of the

    A. T12 and L1 vertebrae

    B. L1 and L2 vertebrae

    C. L2 and L3 vertebrae

    D. L3 and L4 vertebrae

    E. L5 and S1 vertebrae

ANSWERS

54.1 C. This patient likely has an obstruction of the cerebral aqueduct of Sylvius since this is the conduit between the third and fourth ventricles. Thus, there is dilation of both lateral ventricles and the third ventricle, but a normal fourth ventricle.

54.2 A. During the lumbar puncture, the needle will sequentially pass the supraspinous ligament, the interspinous ligament, the ligamentum flavum, the dura mater, and the arachnoid mater to enter the subarachnoid space. The anterior and posterior longitudinal ligament is located in the anterior and posterior surface of vertebral body and deep to the vertebral canal and should not be reached; the pia mater is a thin layer of meninges on the surface of the spinal cord. During lumbar puncture, the needle is inserted below the inferior end of the spinal cord and should therefore not reach the pia mater.

54.3 D. In an adult, the inferior end of the spinal cord is at the level of the inferior border of the L1 vertebra. Therefore, to protect the spinal cord, it is safest to insert the needle between the L3 and L4 or the L4 and L5 vertebrae.

ANATOMY PEARLS

⯈ There are three layers of meninges that surround the spinal cord and brain, and CSF fills the subarachnoid space, which is located between the arachnoid and pia maters.

⯈ CSF is produced by the choroid plexus found in the four ventricles of the brain and flows back to the venous system through the arachnoid granulations. CSF surrounds the central nervous system to protect the brain and spinal cord.

⯈ Laboratory examination of a sample of CSF can help us diagnose bacterial infections, viral infections, and tumors in the central nervous system.

⯈ There are no lymphatic vessels in the central nervous system, and the CSF acts as the lymph of the brain and spinal cord.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:628−630, 632−633. 

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:878−881, 886–887. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 109−110.

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